I sunk 600+ hours into the "worst" version of the game on Switch 1 and never found it that big of a deal breaker, but the good news is this game now holds a near-constant 60fps until late game on Switch 2 without a patch. Further optimisation could theoretically be possible as Devs get used to the new system, but as it stands this is a very playable and enjoyable experience anyway.
Risk of Rain 2 + Survivors of The Void DLC + Seekers of the Storm DLC:
https://ec.nintendo.com/AU/en/bundles/70070000024502
If you buy each item separately I think you may save a few cents. Alternatively the DLC expansions are also on sale individually if you already own one or the base game.
A brief performance analysis on Switch 2 in this video:
https://youtu.be/W7DydmAm4nM?si=yNWAFb_fQavBzrMV