At this point, I have as much flight time in DCS as SFP1/SF2.
Some of the aircraft can be configured/flown very much the same as SF2 aircraft.
Flaming Cliffs aircraft have common systems mapping just like SF2, so you can setup your hotas to accommodate the US controls and/or the USSR controls and pretty much share the same control maps between all of these aircraft.
Older aircraft like the F-5 and F-86 have similar controls to SF2. There is more detail in the operation, but overall, you can fly with just HOTAS buttons mapped.
One aspect of DCS that is the hardest is the startup procedures. Some aircraft are similar and/or easy, but many have long, complicated procedures. There is a keyboard shortcut for startups.
If you air start rather than start on the ramp or runway, most aircraft have all the combat switches in the correct positions, which leaves most aircraft ready to fly air-to-air as easy as SF2.
Some aircraft are extraordinarily complex. There is no getting around all the button pushing. Particularly modern glass cockpit aircraft which have multiple MFDs plus a good amount of conventional switches and buttons.
The A-10C and F-16C are the most complex to me. In theory, the F/A-18 is just as complex with all the displays, buttons, and switches. But I find that the F/A-18 can be flown mostly from the HOTAS and feels almost as easy as the F-5 with more power and better radar/weapons.
The MiG-21 cockpit is intimidating, but the startup isn't too bad and there aren't many switches you need in combat. If you air start or use the startup shortcut, it only needs a little more effort than the other aircraft.
I mostly fly everything from the F-86/MiG-15 to the F-14A. I prefer the SF generation of aircraft and these are they. I also fly the WW2 aircraft, but not as often as I really enjoy the Korea to mid 70s jets. The UH-1H is possibly the most fun module in the game. Once startup is accomplished, weapons are armed, and the gunsight is down and on, it is all about the stick, collective, and rotor pedals. I am not sure how difficult it would be for you using a twist stick and throttle.
If you already have the hardware to run and play DCS, you don't have to waste time asking about it. You can fly each module for 2 weeks for free. Given the number of modules available, you could keep yourself busy for free for many months if you don't start the next module until you finish the two weeks for the current one.
Also, the A-4E-C Skyhawk is available for free. It is a little harder to fly than an SF2 A-4, but it is amazing. At this point, it is as good or better than most of the payware mods. The A-4 is actually helping DCS sell more modules. People that join the Forgotten's Vietnam server to try out the Skyhawk usually end up buying the UH-1H and/or F-5E after seeing what DCS is like and all the fun those aircraft can have in a good environment.