ESL plugins which is the new format of Skyrim SE don't count as a esp -> so all esp that are esl (in MO2 you can see the numbers of esl/esp/esm in plugins by passing your mouse on the number of plugins activated, don't know on Vortex, because I don't use Vortex) don't count in the 255 limit, so you can have a lot more mods on SE without merging them.