if the first UASF/BIP148 block is found on SlushPool on/after 08/01/2017 the chain will spilt. with this low hash power and the high difficulty the next UASF/BIP148 block will take a long time until the "wrong" difficulty is adjusted. but chain spilt will happen in every case on/after 08/01/2017.
But will this second block be a direct successor to the first block (a different prong) or will it just be, say, the 50th block on the unique chain, but the node not taking into account the 49 non-UASF blocks in between, but accept nevertheless the header chain ?
the second UASF/BIP148 block will be a direct sucessor to the first UASF/BIP148 and it will take a long time to find it because the difficulty is to high for this particular hash power on this UASF/BIP148 chain. --> this is the miner part with a UASF/BIP148 node.
the full node part with UASF/BIP148 will just see transactions in the UASF/BIP148 blocks on/after 08/01/2017.