We have a 12 x 23’ pool it is okak for just relaxing in the pool and the kids playing but an endless pool is really the way to go for laps. As for heating we do use solar it works great but our pool is outside. Indoor pools require a lot of thought since the moisture has to be dealt with in the proper way.There are companies that can build your pool to size so maybe check that out.

Rot and mold management is key. Moisture is your home’s enemy. And you’re giving it a gold engraved 300K+ invitation.

Do you have enough room for a proper deck around that pool? Minimum 60”, and that’s small. How do you plan to hermetically seal this room from the rest of the house? The exterior? How do you plan to heat and cool it? It will need its own separate system. The condensate from the heated moisture will condense against the cooler walls, and you’ll need specialty construction to not let that infiltrate the home, or rot the construction. That’s a lot more than building with pressure treated and sticking a motel unit in a window. A LOT more.

Indoor swimming pools are very expensive PIA giant saunas that are usually poorly vapor proofed, and end up as even more expensive rotting structures down the road.

ALL indoor pools should have a de-humidification system to prevent moisture. If not, everything in that room will rot to pieces over time.

Desert Aire is a company that makes these systems. Their systems can be coupled with heating and cooling systems and you can also tie in for supplemental heat for the pool. Part of sizing a system factors a pool's surface area which contributes to the moisture in the room.
An automatic cover is highly recommended to keep the moisture contained.

As far as a suggestion for a style of pool, it comes down to what you plan most to get out of the pool.