The three I recommended are typical Korean-style spas. Admission cost varies ($30/Lux, $35/iSpa, not sure at k-spa) and that gets you admission to both the male-only areas (showers, cold and hot pools, sauna, steam, recliner areas) as well as the co-ed areas (food, lounging areas, additional hot & cold rooms). You leave your shoes in a separate shoe locker at iSpa and KSpa, though not at Lux, and in all places they'll issue you shorts & a t-shirt to wear as needed. Clothing is not permitted in the single-gender wet areas; it is required in the co-ed areas and sometimes in the single-gender lounge areas. Towels are provided - iSpa and KSpa provide unlimited hand towels in the wet area, while Lux issues one bath size and two hand towels upon admission and doesn't make additional towels available in the wet area.
One thing I sort of overlooked in the original post - OP was looking for a place where he could enjoy both a clean facility and naked sex play. While cruising behavior certainly goes on at all three of these places, they are not generally places for "naked sex play". ISpa and KSpa in particular often have a family crowd - literally dads with their sons - and personnel keep reasonable tabs on the facility. Somewhat less so at Lux, and a fourth in Norwalk that I didn't mention called Pioneer Spa, but please understand that these are not gay bathhouses.
KSpa is the newest and cleanest - iSpa and Lux are somewhat older but still maintained well for the most part.
I hope that helps.