Testing layers: (should be done in 1-4 working hours).
Logic: does new features reach the goal;
UX: do 3-5 users to reach the goal;
Languages (and grammar): test at least with 2 languages;
SP: 2 languages (product and data): 1) native 2) one of: RTL, Chinese, Italian.
Plans/Access: test with different plans (if needed). How different plans see the same feature;
UI: does it follow our UI principles;
Devices and screens:
3 devices: desktop, tablet, smartphone (browserstack.com);
2 browsers: Chrome, Firefox, Safari, Edge.
Monkey test: different key combinations and shortcuts;
Maximum (most important):
Unit testing: for most important tasks;
Stress testing: small DDos, high-load;
Security testing: bounty hackers.