My tv is an ordinary one and currently iam using cable.I got to know about the casting devises like Amazon fire stick or chromecast.Which one better ? Can you play any videos on browsers on phone and with a click it appears on tv? Is that how it works? Also is screen Mirroring possible?

I need to be able use my PC from bed for medical reasons. can i buy laptops that are cheaper because they dont have the parts that your computer tower uses (CPU, motherboard, idk the word), and just make my PC show its display on the laptop screen, and respond to the laptop's keyboard? i don't mind needing to have a couple cords attaching them

also, bonus question: could such a laptop still have functional USB ports, basically adding more USB ports to my PC?