It does use more power and may lead to burn in depending on the content you’re watching. Personally I think it looks bad but if you like it it’s your TV do what you want

If you can get it for a good price, sure. Factor in the cost to replace the battery if need be

I recently got a used S21+ from eBay for $220. Happy with it. Battery still at 94% original capacity. No scratches or scuffs on screen or body.

If you don’t game and don’t need the best camera, older flagship phones do fine. One UI hasn’t changed much either

Heck I was happy with my S10+ till it died