Suggestions for high end Springer?

My background...
I have been shooting for a few year with a Crosman Nitro Venum and later a Walther Terrus, both in .22 cal. The Crosman 'helped' cut down the squirrel population in my yard. 200 squirrels later I don't see too many and now mostly shoot targets. I can shoot pretty accurately with the Terrus but it seems to be inconsistent at 50 yards, that is, sometimes I can hit a 1-1/2 spinner consistently, other days not so much. I feel like the trigger release is a little stiff and throws me off. I can get hole in hole at 25 yards then one goes off a little. My goal is 1/4" CTC groups at 25 yards and 1" or so at 50 yards. I am using H&N FTT

Q 1. Are these accuracy goals realistic with the Terrus and how can I get better?
Q 2. What size groups can I get with a high end springer? I have the itch to step up to a better gun and want to consider buying one.
Q 3. I am considering the Walther LGU and LGV as well as the HW 97k. I know it has been asked before but I would like your comments on best choice. I value accuracy (out to 50 max), trigger and getting a good rifle without having to rebuild/tune at the outset. Don't want it to be finicky to run over time. Weight not an issue. Beauty not quite as important. 
Q 4. Are there others I should consider?
Q 5. Will a thumbhole stock help with smooth trigger release. (again, I feel that is a weak point now)
TIA!
 
Well, I have the LGV in .177 and I think it will do what you want. Check it out below. There are other guys here that have one too and can shoot it much better than me. 

https://www.airgunnation.com/topic/intenseaty22s-walther-lgv-master-pro-177/

As for the Terrus, I have no experience, but I would recommend taking it appart, clean it well, consider a Vortek or Maccari kit. 

The TX200s & the HW97s are fine guns with great reputations. 
 
I own the following:
Air Arms TX 200 .22
Air Arms ProSport .177
Weihrauch HW 77K .22
Weihrauch HW 97K .22
Weihrauch HW 95 .177
Weihrauch HW 30s .177

All my springers keep up with my PCPs at up to 35 yards or so. Past that distance and I can't shoot them as well as I can my PCPs, not the fault of the gun. 
I prefer .22 cal to .177 mostly because the shooting cycle seems more muted/less harsh when shooting these higher powered springers.
I prefer the trigger on my Air Arms vs Weihrauch because the trigger itself is further back in the trigger housing, but both are excellent. 
I prefer my TX 200 in .22 more than my ProSport in .177. The TX 200 is easier to cock and shoot for longer sessions. 
 
I own both a Pro Sport and LGU in .177 and they are tuned to 12 ft. lbs. I have not missed the small amount of power I gave up. Both are Damn accurate,more pleasant to shoot And a breeze to cock.

I'd like to mention my Diana 54 in .22. Power to spare and so easy to shoot well that it's almost like cheating! Beautifully engineered rifle and there are many,many people that will say the same! The Diana 56 is the same action in a nice thumbhole stock. I would really like to get my hands on a 56 stock for my 54. Same as You,weight isn't an issue as I usually shoot this one from the bench with a bipod.
 
I would go with a HW 95 OR HW 98 in break barrel... The Terrus maybe a little low on power for 1 at 50, however at 35 yards 1" is doable...The biggest problem with accuracy on my Terrus was not me or the gun, I can blame it on the trigger, so I polished the trigger and removed the main trigger spring and replaced with a much lighter spring...After that I have just over 1 lbs as a trigger pull, the gun is extremely consistent on Velocity...Mine is 177,,

Here is a diagram of the trigger...

1529981515_5861329175b31aa4b3240f4.54775562_tune trigger.jpg


Here are some groups at 30 yards

1529981659_12557637715b31aadbb1d512.48586536_20180513_170234_resized.jpg


1529981670_18427308165b31aae6604b44.72509568_700 pellets.jpg

 
I got the HW97K from here new for $360. I dont have alot of experience shooting springers but on my first day I was shooting 1 hole groups at 35 yards. I only had a 9 power scope though so my 50 yard groups were not as good. Best value out there though and one of the best trigger. They sell for $600 in the US. Krale will ship to you for $42.00. Here is the link: https://www.krale-schietsport.nl/en/weihrauch-hw97-black-line-stl-9331.html
 
I have a Trail NP, not much different than your Nitro Venum. I ordered the replacement trigger before I bought the rifle. The trigger is about one pound with a nice wall that breaks clean. It is .22. If it was only three pounds lighter!

It has a sling on it. If I put the sling over my left elbow, and grasp the last three inches of the strap in my hand, not the stock, with my arm on the bag, my rifle will put five of the Ruger Superpoints in about half an inch at 30 yards. Pretty close to that bracing the fingers of that hand against a tree around the strap, and pulling the strap tight with my elbow. If you cross your fingers and hold your mouth just right, at thirty yards you can hit the last hole off the bench with the X-Match wadcutters, and that is with the included scope.

A buddy came up with some older Gamo Magnums that shot okay, but you could not adjust the scoipe without shimming it. They were pretty heavy..

Warning. If you try to shoot holding the sling like I said, make sure to take sand paper and debur the bottom of the cocking slot area of the stock. If you don't, the recoil will make little cuts in the top of your thumb each time you fire it from the mold lines.

My old eyes can't hit small targets at 50 yards, so 30 yards is just fine.
 
Welp, one hole groups with a springer at 25 yards are possible, but not bloody likely. If someone tells you their spring gun is shooting one hole groups at 25 yards ask them to prove it.

We need some perspective on what is possible, what is probable, and what is exceptional in a spring rifle.

I think it is time to resurrect this thread: https://www.airgunnation.com/topic/ten-dimes-challenge-changed/