SegWit (the original proposal which I believe was BIP141) needs 95% to activate. it is the well thought plan, tested, needs the majority to support it to activate. it has practically no risk of any split or any danger to bitcoin.

BIP148 has no percentage. it is rushed and in my opinion not even well-planned. it is forcing the miners to switch by rejecting their blocks if they are not signalling. it doesn't need much miner support and the higher support it can gain the lower the risk of a split will be.
so far it has so little support from miners and there aren't that many nodes running it either.

SegWit2x needs 80% support to activate SegWit, I believe they are going to use the same version bit for signaling and this means if SegWit2x gains the support it needs BIP148 won't do anything because it sees the blocks as signaling what it wants.
the support is so far between 85-90% but it is only in their text that they include in the coinbase transaction. they have to start with the version bit. which I think will start on 21st.