I think a lot of it has to do with the tube/speaker/pickups. In other words there are a lot of variables. What you are describing is why a lot of guys go to pedals to shape their tone. I think your fender is a 4/10 combo and probably has GTs in it. Fenders have always been known for their extreme cleans. A Marshall on the other hand has decent clean tones but is a little more forgiving on the clean channel. Of course we all know about the Marshall OD channels.
So I would say that yes some amps are more forgiving. Fulltone has a pedal called a fat boost that thickens up the tone quite nicely on Fenders and single coils. I would say you can tweak your Fender with pedals etc. to get a "clean" yet forgiving tone.
If you check out Gregory Hilden's videos he uses a Fender Vibrolux reverb which is a 4/10 but he always uses some sort of OD. He get excellent clean tones from any of the guitars he reviews
Sorry I have no experience with Peavey but you seem to like that tone anyway.
The Blues is alright!
Guitars: 1968 Gibson SG, 2005 Gibson SG Standard, 2006 Gibson LP Classic Gold top, 2004 Epiphone Elitist LP Custom, 1996 Gibson Les Paul Standard. 2001 Epiphone Sheraton II, 2007 Epiphone G400.
Fender Strats: 1996 Fender 68 Reissue CIJ, 2008 Squier CV 50s, 2009 Squier CV 50s Tele Butterescotch Blonde
Amps: Blues Junior Special edition Jensen in Brown Tolex with Wheat front, 65 Deluxe Reverb reissue,1970 Sonax reverb by Traynor, Avatar Custom 2/12 Cabinet with Eminence Legend V1216 speakers,
2008 DSL100 Marshall Amp , Fender Super Champ XD,Fender Vibro Champ XD
Effects and Pedals: Fulltone Fulldrive II, Fulltone OCD, Fulltone Mini Deja Vibe, Fulltone Fat Boost, Dunlop Crybaby Wah, Boss DS1, Boss DD20 Giga Delay, Boss TU2 tuner, Boss BD2, Ibanez TS9 Tube screamer, Zoom 505. Radial tonebone hot british.