Disabling OTA updates and enabling wifi tethering are two completely independent things. A ROM might do both for you, it might do neither, or it could do either one and not the other.
There are LOTS of options for which ROM you can pick if you want to go that route. Most will do both the OTA update blocking and installing a custom kernel (to allow wifi tethering), but you will want to check with the feature list of that rom. Wifi Tethering is not a ROM, but a feature that some roms include.