Beaver_XT The 4-in-1 has more receiver compatibility. For example you can bind it directly to Mini-Z (the FHSS with white antenna), WLtoys K989, K969, 284010, 284131, SNT micro cars, Flysky AFHDS and AFHDS 2A receiver, Radiolink and DumboRC receivers, etc. ELRS version only supports ELRS receivers, which are many to choose from. But you are limited to the ELRS protocol. Unless of course you install a 4-in-1 module to the transmitter. You can also install ELRS module on 4-in-1 too so basically just choose which one you will use the most.

Beaver_XT The 4-in-1 multiprotocol version supports many protocols (receivers). For example you can bind it directly to Flysky AFHDS, AFHDS 2A, Radiolink, DumboRC receivers or you can also bind it to WLtoys cars, Mini-Z cars with FHSS protocols, etc. This version comes with 5 channel receiver called R85C. It's a receiver with FrSky D8 and Futaba S-FHSS protocol. More protocols are available, search for pascallanger DIY-Multiprotocol-TX-Module to see if there's anything you use. The ELRS version is the ExpressLRS version which is an opensource project. It boasts the latest and greatest communication technology with ultra low latency (rapid response, I tested mine and it's about the same as Noble NB4), long range, good penetration (basically for FPV flyers) with fast support or troubleshoot from opensource community. The receivers are widely available from different manufactures that make drone receivers.

Beaver_XT 257mm wheelbase 190mm width Exactly the same as Tamiya TT-01

Beaver_XT Yes, this works with stock diff. At least the batch I got worked.

Beaver_XT Yes, the latest version of multiprotocol has Radiolink protocol. It's Radiolink surface.

Beaver_XT Any 2S lipo not exceed 400mAh will fit nicely and get a JST-XH 2 pin plug for conversion as well.

Beaver_XT No, it does not.

Beaver_XT Yes, they are.