If you like the 6D2, then go for that. The Canon Refurbished Store can run out of stock on attractive deals very quickly.
You have to decide if your mirrorless or DSLR. In your position, I would want the mirrorless, but not the RP. It is too small for my big hands.
If you go FF, the only lens you will walk away with is the 50mm. I personally am not a fan of any Canon mirrorless body's. I am pretty biased here. For me, each one has compromises that I cannot accept.
From top to bottom:
Touchbar vs. joystick
Low MP count
Overpriced, over heating, atrocious recovery time, super duper still image capture device
Don't get me wong. I am a Canon user for life, but am still waiting. I guess for 4th or 5th gen mirrorless now.
The truth is you should not let what others would or wouldn't buy influence you. Buy what works for you.
If I was in your situation and still image photography was my primary use, I'd buy a 5D4. Christmas is just around the corner and it will be going on sale (refurb and new).
If it wasn't in my budget or if that budget had to include one or more lenses, then the 6D2. Its a great camera (and not because I own one).
If you must go mirrorless, then the R. Since you have never had a joystick you won't be so bothered by the touchbar. Again with emphasis on still image photography. 30MP which is comperable to the 5D4, and 4MP more than a 6D2.
(R6) Consideration - 20.1MP - The level of detail is adequete, but not enough for me since I'm already at 26. I can't go backwards. Now however you have the potential for overheating, lengthy recovery time and the possibility of not being able to turn your camera on when you need it. I take my camera outside in temps above 73* and if I couldn't shoot just once, it would take all of the happiness and enjoyment out of a canon product I have come to count on. For me, (and others) its all about consistent, reliable performance.
You are going to get that on any of Canon's standard DSLR's. No compromises, No might or maybe's.
Check the Canon Refurb store for deals:
mstu33- I got the R for very similar shooting to yours. I'm a high school theatre teacher, so mostly people on the move, and I also shoot a lot of landscapes and architecture for fun. And it's been working out great!
BUT here are the things that are making it work great- at added cost:
-the RF 24-105 f4L kit lens, which is awesome
-Topaz Denoise AI, which is $80 but worth it for the kind of shooting I do. This camera gets great results up to 12800 ISO, with this software.
-Lightroom- not free
A lot of people on these forums have much higher standards than me, which is great 'cause I learn a lot. But I have very few complaints about this camera.
It does have crazy dynamic row noise, if you push things up multiple stops in Lightroom. I'm irritated about that, so if I start doing more star photography, I might upgrade to the R5. If it proves to be a lot better. If.
The OP mentioned the R and RP. I recently bought an RP and I love it, especially coming from the T6. But I did a lot of research first, and I was well aware of its shortcomings -- abysmal battery life, a paltry 5 fps max burst rate, good but not great weather sealing, generally higher cost of RF lenses, lack of in-body image stabilization. So why did I buy it? I wanted to get into mirrorless AND full frame at a reasonable cost. The issues I mentioned were not deal-breakers for me. I paid an on-sale price of $999 for the camera, kit lens (RF 24-105mm f4-7.1 IS STM lens), and a bunch of accessories including a camera bag. I have zero complaints. I expect to have the camera for a few years while I acquire more RF lenses. My next two lenses willl be the RF 70-200mm f4 L IS USM (the smallest and lightest of its kind ever developed, I believe) and a 16-35 for landscape work.
Personally, I don't recommend anything but mirrorless for those contemplating a new camera. If you're coming from a T3 you will be blown away by mirrorless tech, I assure you. The EVF tech in itself is a huge advantage. Some people don't like EVFs, but I adapted quickly. Frankly one of the bigger surprises of the RF for me is how easy it is to hand-hold steadily and get tack-sharp results, likely due to its smaller size, light weight and lack of mirror slap. It's great for all-day carry out on the trails and in the SoCal desert. YMMV but best of luck no matter which way you go.