Finally finished my first day. The result (in UTC Time) :
3-2 (22:00)
4-1 (4:00)
5-0 (11:00)
5-0 (14:00)

I met no whales, the best deck is MLB Kita/Creek borrowing the other one.
Met 11 tryhards (umas have good stats, skills, and sometimes turf/medium S, nice composition team).
15 prepareds (umas have enough stam, but bad skills or low stats).
14 casuals (auto-select).
15 people bring evil nature, and only 2 matches with 2 evil natures at a time, lower than I expect.
For me the hardest matches are immediately after the start. The first try gets me most tryhards. You may try to enter a bit late for round 2 (not guaranteed)

Overall pretty satisfied with my golshi's performance. Lone Wolf procs too often for Golshi.
Win against tryhards are mostly from good mood, and activating more accels than them. My only loss are from low mood, blocked, and few debuffs.
Next day I'll try to swap Nature for my Rudolf as third ace/debuffer.