Well for starters the memory controllers are smaller on the series s.
Its also 8 cores vs 4 cores.
The Series S also packs 24 CU. With 20 enabled for gaming. The steam deck has 8 CU
For reference the series x has 52 out of 56 enabled. the Ps5 has 36 out of 40 enabled.
64 bit is quite litterally 2^32 times larger than 32 bit.
There isn’t a need to go to 128 bit yet