There has never been a moment that I did not enjoy playing though the RA100. I would agree that the guitar does make a difference. I have several to choose from and there are a few that just ring out the right flavor of this amp.
The following are all Carvin Guitars (actually the only other brand of guitar I own that is not a Carvin would be a Martin 12 acoustic)
Bolt C (SSS loaded with Seymour Duncan Everything Axe pickups), body wood Black Limba with maple top, 5 piece maple and walnut neck with maple fret board. Bolt C (HSS loaded with Lace Sensor Hot Golds), body wood Alder with maple top. Same neck as above. Both would be classified as super strats, probably would not like them as much without the Floyd Rose. CS (similar to Les Paul) mahogany body and neck (more than likely chambered) maple top, ebony fret board. I have also played a friends Mexican Strat and sounded great once you get past the pickup noise. I also have similar DC400 (neck though type strat body, maple neck and walnut body. I personally prefer the bolt neck type guitar though both the RA100 and Roadster.
Generally I play without any effects except for the built in spring reverb. However If I am going to mix this in a project I will use a delay in the loop and on occasion I will also pull out the Mesa 5 Band EQ if that works out.