I think that of what you speak (Laylax is a brand made by First Factory if I'm not mistaken, their springs are SWEET...... I've a Laylax 150SP in my M24, cocking it is very light and smooth for what it puts out; PSS I believe is a reference to the gun it works in or something, I know PSS2 is APS-2 compatible)............ the strength adjuster (got a link or a pic? ) most likely allows you to add or reduce the about of compression on the spring, kinda like adding or taking off a bearing spring guide. I've seen a set of washers on WGC I think that you add into the piston to compress the spring more for a bit higher fps out of it. I wouldn't say that you can quickly adjust your power in the field with it (like I said, hard to say without seeing what you found), but with the right tools on the hood of a car you most likely could adjust it in about 10mins or so. That's roughly how long it takes me to open my CA M24, pull the spring out, put it back in and get back to shooting. Takes only a couple allen wrenches and an adjustable wrench. Much easier than trying to do anything with an AEG!!
43 meters isn't bad if your gun is stock, that's 140ft. Might be able to do that with my G19, have done that with my MP5.
Should work to get it up to 60m, 200ft, then you'll have some fun!