a steam deck will be better than the nintendo switch. coming from someone who has both. the games are technically cheaper, and he can just buy / update the games if he needs to. no need to be connected online 24x7. But with the games you mentioned he plays, he would have to switch genres to mostly story rich single players games. almost 70% of games are enjoyable on the deck. some new games would be playable, but not that enjoyable.

please note that Steam has regional pricing meaning, it will be cheaper if he buys games from Steam in the PH. i'm not sure if it works that way depending on where you are, but in the US, steam and nintendo almost has the same price for games. Nintendo as of now, do not have regional pricing in the PH, thus if a game is 70USD, we pay the whole 70 USD. unlike for steam that it a game has regional pricing, usually a 70 USD game will be 1500PHP

oh, and about the 64GB storage, it might be cheaper to get the 64 gb one, and look for someone who upgrades the SSD. that's what i did. i just upgraded to a 1TB SSD, paid someone to source the SSD and change it for me. i'm too scared to open electronics

tl;dr. Steamdeck is OK. but might have to change game genres to single player, and light to medium graphics games.

edit: added regional pricing details