which custom field type to use ? or any suggestion ?

Priyank

to categorize/group on jira based on a criteria (which has 400+ options to choose from, and growing) what's a best customField to use ?

We've been using labels, which we know is a pain - and can loose standard - (random ex - MSTeams - Microsoft Teams - Teams)

Any suggestion, what type of customField can we use?

Nic Brough -Adaptavist-

I'd look at the cascading select list, it can break your main list into logical groups (example might be "country -> region", so you'd list USA/States, UK/countries, regions or even counties, and so-on)