I've got the same gun. I only use glasses or goggles. So I have no idea how well the mask would work with the scopes i have.
Normally I run the Hensoldt model 1, I got it for a good price but normally there a hell of a lot of expensive (£450+). It's the correct sight for the gun. Eye relief is correct for the gun dimensions so you have to be right up to the scope, and it is a raised sight using the stanag claw mount.
The other sight I use a fair bit is the Enfield 1.5-4x30 using a rail adapter. There are cheaper alternatives that have the same spec. Enfield as a brand is part of Armex who do most off the Umarex gear. Have a look a visionking as well as they offer the same spec.
https://www.solware.co.uk/enfield-15430-mil-dot-scope
https://www.ebay.co.uk/itm/Tactical-1-5-4X30-Rifle-Scope-RGB-Tri-Illuminated-Mil-dot-Reticle-PEPR-Mount/272990142338?hash=item3f8f7aff82:g:Y2cAAOSwu29ak6~5
I know my Enfield is decent. Good eye relief, very clear. You can pull the eye quite a distance back and it works perfectly. It just lacks a front element coating so you can see the dot from the business end. I had the option to test mine in a gun shop, Mil dot is precise, 3 colours, and the lines are perfect colour overlays of the non illuminated parts. Other walthers branded umarex scopes have also been good for me, I have a ps22 and a ps55 both are very good value clear optics.
The china part one might be a second, or it might have cheaper glass inside, or it might use a cheaper mildot system, there is no way to know until you hold and use it. So If you get one it is a gamble!
With a rail adapter you can use any scope you want. Just get higher risers rings like you would for any rifle. It's not something you should worry about. I'd get a rail adapter then take the LCT to a gun shop and test various scopes till you find one you like.
If you are adamant you want to use a stanag claw mount then look for one with the 22mm rail upper. Leapers/UTG make a clone of the H&K mount for about £80. It may need modification to fit the LCT. On the original there is a removable rubber pad on the back of the claw, It needs to be removed for the claw to work on the LCT. Some of the UTG/leapers mounts have that rubber pad cast into the mount. If this is the case you will have to file it off for it to fit.
https://www.amazon.co.uk/UTG-STANAG-Steel-Claw-Mount/dp/B002GNYCLM
