The BTR and CTR are RR based. I know the CTR has always been RR, though I think I've seen pictures of AWD BTRs....
AWD is optional on 964 and 993-bodied BTRs. Naturally, really, as the coresponding Porsche models also have AWD option.
A curious addition to the lineup is the RCT, which in 964-bodied, and
was sold alongside the 964-body BTR, even though the spec was
almost identical and also with optional AWD...
Main difference between BTR (930-guise)
and CTR is that the CTR has twin turbos where all the BTRs have a single turbo.
The CTR2 is AWD 993 turbo based
Again, AWD was optional BUT, nearly all CTR2s were specced as AWD.
The "R-turbo" replaced the BTR with the 996 chassis RR or AWD (depending on what the buyer wants) car.
It also replaced the 993-bodied Turbo R... (Had 490 hp and Turbo bodyshell,
power-wise it's the closer match to the newer R-Turbo, hence the name too)
The RGT is the NA engine 996 based RR or AWD (depending on what the buyer wants) car.
This is practically a RUF version of 996 GT3 RS, in fact it uses some of the RS's body panels fitted to a GT3 bodyshell - the GT3's bodyshell is stiffer than Carrera's.
No offence intended - you probably already knew all this stuff... Why I posted this is just because I'm a huge Porsche and RUF fan.