Welcome to the forum!
You're right there aren't many electric guns with 'recoil' (really just a vibration, but a lot more fun to shoot)
There's the Tokyo Marui 'Recoil Shock' range, but they're ~ £450+
Bolt, but apparently they break quickly (ERG RM4 is nicer anyway)
Lastly will mention G&P. They tried it but doesn't seem to have been very popular at all (the recoil feature seems non-existent)
Downside with the PTS ERG is that I don't know anywhere which has them in stock anymore? Maybe Redwolf...LWA sold out ages ago then suddenly had 2 or 3 back in stock again - went quickly
Also if you wanted to swap out the handguard for a RIS there's no space for the battery so you'd have to use a battery box like an AN/PEQ-15 replica
KWA were supposed to release a new rear-wired version but never did
G&Gs are definitely a good choice as a starter gun, can't go wrong with them at all (I only know ONE exception which is the M416s -called the T418 I think- which come with sh*t MOSFETs)
Depends what your budget is really...
I'd like to say that parts were interchangeable as with real M4s but really aren't
Some guns will be very specific with which magazines they will take (as in how well they actually fit in the magwell and the feeding etc)
On my sh*tty CYMA M4 I have tried a PTS ACS stock but it wobbles a lot, yet would probably work fine on a G&G and others
You'll probably have most problems with cheaper guns as the better quality rifles are made to more accurately to exact dimensions and tighter tolerances closer to real firearms
Hope this helps and it's alright to repeat stuff, it happens all the time from beginners and experienced guys
It's a complicated hobby + people learn about guns themselves and all the different airsoft manufacturers and then there's regulations we have don't help - probably puts a lot of people off and especially with the amount of misinformation that goes around about it being a licence and so on