Hard to beat the price on the Diana guns you are considering. I can't help you there and if you are handy in the least they will be fine. I think I only get one or two complete fills on my impact with the Ninja tank but when the pressure gets down to 3600 I just tether it and shoot and shoot and...
As far as tips for using the Yong Heng you have come to the right place. ;^) I have two and have been running one or the other for three years now with only minor problems for the most part.
Edited and Current 3/21
Here is my standard post to all things
Yong Heng hope it is helpful.
The Yong Heng "
Simple" version least expensive does not have a water separator you need one.
The "
Auto Stop" version shuts off near 3000psi probly
not a good thing for most people.
So you likely want the "
Hardcover" or "
Set Pressure" versions your choice on the 110V or 220V.
https://www.aliexpress.com/item/32824234795.html?spm=a2g0o.store_home.productList_13760454.subject_2 Never start them under pressure. I should have put this in here sooner.
Give them a dedicated 15amp outlet 20 would be better. They draw a bit of juice on start up especially the brand new ones. Don’t Use an extension cord unless it is short and has an honest 15+ amp rating. Preferably 12ga wire so you will not have problems.
Keep them cool and filled with oil.
ISO 46 may no longer be recommended although I used it for a year without failure. I am currently using the Husky Brand Synthetic or synthetic blend oil, found at Home Depot, for two years now without a problem. Top it off to the red circle in the sight glass.
Don't push your air fill past the compressor’s spec which is 4350psi. A little
less is usually better than the max, and the Yong Heng should last for years unless you get a bad one.
I did my first oil change at about an hour, it was extremely dark colored. I went far longer, between changes, after that.
I have two YH compressors bought the second as a backup for the first as I, fergot to turn on the coolant pump several times and, overheated it until it smoked. It did not like it but it continued to run just fine. Still I did not trust it after that. I
added a switched outlet, to the system, so it turns the pump on before the compressor will power up to keep me from doing that from now on.
The second one, my back up unit, died in about two months bad QC from the factory. Cost me $12 for a new second stage piston and an hours’ time to replace it. Then to add insult to injury I fergot to put oil in, the latest unit after I put it back together, and ran it for a couple of minutes without any. So I filled it with oil and it fired up and somehow still werqs fine. The #1 unit that I was worried about, cuz I overheated it so many times, just kept on filling my guns and tanks till I got #2 repaired and retired it.
I do not fill past 4200psi as when I do, all too often, I blow a burst disc. This may not happen on the first or second fill but soon thereafter it will.
The temperature sensor
only measures head temperature so running it much over 20-30 minutes can overheat the motor and other parts even if ice is used in the coolant. Ice or a container of it, in the coolant, is a good idea especially if you are like me and do not use the full five gallons of water as suggested in the manual.
Keep your water supply level with the compressor to
be kind to the pump and assure a good supply of coolant goes through the compressor.
I recently started using this Red Line water treatment after I noticed algae growth in my 2.5 gallon water bucket every few months. It seems to have stopped or significantly slowed the algae growth. I will know more in a few months.
https://www.autozone.com/antifreeze-radiator-additives-and-windshield-wash-fluid/coolant-water-wetter-additive/red-line-water-wetter-super-coolant-12oz/486218_0_0 Keep your moisture filters, guns and tanks being filled above the compressor to
help keep the moisture out.
Purge the system of moisture,
using the screw valves on both sides of the compressor, for a couple of seconds
every five minutes while in use.
Change out your small YH filter
every twenty minutes and set the old one out to dry and reuse later.
Add a better filter if needed to be sure more moisture and any oil smell is removed from the system. Many of us use this
Tuxing three media filter although, if you feel the need, you can change media types at any time.
https://www.aliexpress.com/item/32891898253.html A smaller one will probly do for some.
https://www.aliexpress.com/item/4000960926898.html?spm=a2g0s.9042311.0.0.2a034c4dL0nrJU Possibly a filter similar to this if humidity is high in your area and your desiccant filters have to be replaced often.
https://www.ebay.com/itm/30MPa-High-Pressure-Air-Filter-Oil-Water-Separator-For-Air-Pump-Air-Tank/402600939671?hash=item5dbce2d097:g
RoAAOSwy41f00pY Bleed the pressure before you turn the unit off and let it run a few seconds to get the better part of the moisture out of the system. I have found that I blow less burst discs if I bleed before shutting down so I do this religiously.
Let the coolant pump run for a few minutes after shutdown to cool things off.
Info on the radiator install.
https://www.airgunnation.com/topic/yet-another-yong-heng-mod/?referrer=1 Here is a video on how to fill a SCBA tank.
https://www.youtube.com/watch?time_continue=157&v=_grx5p_R8D4&feature=emb_title 
I do have some spare totes I could rig up for water cooling the compressor, but I can't have a permanent setup like you have. Our house is small with no garage or basement for that kind of thing. Some day we may get scuba certified, so in the long term I may do it. I have a feeling if I want to tether the ninja tank to either our seneca or the diana then both will need a regulator since they aren't rated for that kind of pressure. That puts the Diana at nearly $400 from Pyramid (with them doing the work), but I assume it would be a pretty competent rifle at that point. Does the Diana require some kind of quick connect fill probe to work with the quick disconnect on the compressor? 
I saw a video where a guy pumped up his bandit, for a staggering 30 shot string, with just twelve pumps on a hand pump. Amazing. I figure that 12v capable pump would hold up pretty well under those kind of conditions! If it weren't such a hike from the house to where I shoot the YH compressor would make more sense.