It's adjustable. It has a dwell screw on the side (goes into the valve) that sets the power and the hammer spring adjusts the start of the curve.
I have tuned mine and two other guys rifles for various bullet weights and like any pneumatic airgun, you can get high power first shot and a declining shot curve (usually with high air consumption) OR start off with a lower first shot and a flatter curve.
With a 148gr going for highest power 1st shot I've gotten 989, but the next shots were always way down like 910/920 and third shot was low 800s.
Retuned to start around 945/950 it has a much flatter curve and the first three shots are usually very close together. This is good enough (to me) for a hunting rifle. Rare in my experience to be shooting more shots than that hunting either hogs or deer.
I've tuned for a 130gr and 950 FPS and gotten a nice 6 shot bell curve before it really dropped off.
I don't know anything much about the .452, same gun but different barrel I guess.
I am right handed and right eye dominant- I have a Pitbull 'bullpup' and the RH Slayer and I found with both that shooting in any position except the bench (like offhand) I had to move the rifle too much off my shoulder to reach the bolt and cock it. The Benjamin Bulldog/Pitbull can be changed to either side so I've tried it as both and found that it is more comfortable to keep the trigger hand on the pistol grip and the rifle shouldered and use the left hand to reach up and cock/load. So I ordered my second Slayer as a LH.
Cleaning - wow, that's a LONG discussion and LOTS of disagreement between individuals. Ties into the Pandora's Box of "lubes" on slug guns (pellet rifles are different, they don't foul near as much!)
Here's what I personally think after 50 years if centerfire pistol and rifle shooting and a decade of high powered pneumatic shooting experience. I lube to try to prevent leading/fouling and if I'm at the bench I might use a wet lube / oil (10wt synthetic RadioControl shock oil is popular, search for many discussion on the many lubes used).
BUT, I don't want a messy oily bullet while I'm out hunting in the field. So I use either FinishLine Wax Chain lube with a dusting of Hexagonal Boron Nitride (White Graphite) or Rooster Jacket bullet coating and the HBN. I did not get the accuracy with the powder coated bullets but have gotten better results with diluted/thin Hi-Tek coating.
Unlubed, I've seen cast and swaged bullets lead up a BigBore barrel (.257 to .51) in 50 shots in a rough barrel, 200 in a smooth one. With a good barrel, and maybe polishing/firelapping* and using the right lube : I don't get leading at all in hundreds of shots and keep the accuracy.
My pellet rifles might fire 5000 shots before needing cleaning (I've got a .25 Synrod that has twice that through it and still does not need cleaning and is accurate) but I wipe my BigBore slug guns with a damp patch of Ballistol (50% water / 50% Ballistol) every 100 shots or so and at the end of the days shooting besides the bullet lube.
If I encounter a fouled barrel, I first use a jag, not a slotted tip and using "chemically treated lead removal cloth" (I like the KleenBore Lead Wipeaway) cut a patch and run that TIGHT patch through the bore 10 or 12 times, flip to the other side and do it another 10 or 12 times, back and forth. Wipe the bore with a clean patch to get the residue out, then I use a brush and Ballistol to do the barrel.
I ALSO do this to new to me airguns or ones that I'm cleaning for others that are badly fouled or prone to fouling.
* I coat the nose and sides of either pellets (45 or 50) or slugs with a bit of JB Non-Embedding Bore Cleaner and shoot them. Note this means cleaning the moderator so if it's got felt I take that out first! This is a poor man's bore polishing and does not hurt anything but rifles don't foul as fast after you do this.