I'm having a grumpy moment, so...
It's not balanced. The details state "MP-701 MK2 is based on single ended circuit. XLR is converted from RCA for convenience, so user can use existing XLR cables". In other words, it's single-ended with XLR sockets glued on.
WRT the tube rolling, anything that can use 6N11, 6N1P, E88CC, E188CC, 6922, 6H23, 6H6, 6H30, 6SN7, 12AU7, 12BH7, E80CC, and 12SN7 will sound different between the different valves for sure. Not by virtue of 'rolling', but because most of them will be running way outside their optimal point. A proper circuit is designed for one type of valve, or (very) near equivalents.
It's a valve effects box.