Sounds to me that you are after a roomy tent but just for yourself.
I look after Tarptent in Australia so I am pretty familiar with all of the models and have used most of the solo versions myself.
I don't really have a favourite , but for you I would suggest the Rainbow.
It is large enough to take 2x 20" mats , you do that by sacrificing a bit of the bathtub height.
So more than enough space for a solo hiker that likes to spread his gear around.
No it will not keep you warm , your clothing and sb should do that.
Warmth in a tent comes from trapped body heat and your breath, that can become condensation.
It can be "invisible" inside a double wall tent but it will still get your sb damp.
If you use trekking poles you could look at the Notch with a "solid" (fabric) inner that will help a bit more with wind.
(can take a 25x77 mat (just...)but also has two good size vestibules.
Franco