What's the maximum number of Http/1 parallel connections in Population to open requests from application simultaneously on remote server by each VU.
There's no limit on NeoLoad configuration side. However the default settings is most of the time 6 or 8 for all modern browsers. If you would like to run realistic tests i would not recommend to increase that value.
If you still do it be careful as the number of maximum connection on a machine might be reached pretty quickly depending on your scripts.