Mixing FPP and AS for programming FPGA

It's unusual (except for Dev Kits that allow to experience different techniques) to have more than one configuration scheme implemented in a design. In most cases, it doesn't make any sense, to my opinion.

FPP or flash storage with MAX II configuration controller are preferable for larger configuration files, e. g. more cost effective. I'm not sure, if device programming is considerably faster. Configuration itself is faster, but also isn''t an issue with AS for most applications. But your requirements may be specific.

Regarding remote upgrade, the rich choice of options and operatig modes is possibly confusing at first sight, but the technique is documented verbosely in device handbooks and application notes.

Remote upgrade normally implies a user defined communication channel, e. g. ethernet or any other connection already existing in your design as a parallel or serial databus. If none exists, you probably don't need remote system upgrade and could use a local JTAG interface as well.