I think I lost the crypto I had in my stormgain exchange account (StormGain has migrated its operation to the platform powered by YouHodler)
If they did not shut down their exchange, but is migrating to YouHodler, perhaps StormGain team will give their users a window time for migration.
From now on I think I will only use exchanges that are on the top 50 or 100 by volume... or if you have other suggestions/filters when choosing an exchange?
Top 50 or top 100 in volume (trading volume) is not important and unsafe. You must know that Centralized Exchanges are very risky and many CEXes died with time by many reasons, hacks, scam exits, bankruptcies and more.
Exchange Graveyard.Reminder: do not keep your money in online accounts.