Steamdeck will be a good remplacement for a gaming laptop and less expensive. Mine is 1 year old. You almost every games work well on linux thank to Valve and Wine, i don’t see any problems with your game. And you can emulate old game on linux but i never tried it.

There is some issue :

• you can’t play kenshi, city skyline. You will need a dock and keyboard.
• some game use a launcher that will block ya from playing it. Hence why some player decide to install windows. Blane the editor, not Valve
• The steamdeck handle well AAA title but it will drain its battery quickly. Elden ring can last 2h i think.

And IMHO, you should never install windows. Why ? To increase linux marketshare so video game editor work on their launcher and make them compatible with linux. And there is plenty gaming console on windows, lot pc on windows. Windows’s gamer have plenty options. So just for this one, we should accept the steamdeck as a linux gaming machine, for once.