Do followers have a preset first ability?

[Netherspark]

Is the first main ability of a follower always preset, or can it be random?

[MrExcelion]

Most don't, some off the ones gained via non-inn do. You can look it up on Wowhead or the greyed out followers at the bottom of that follower tab to check it out

[Mormolyce]

If you scroll down the follower list to the ones you haven't collected yet you can see an ability/trait if it's fixed.