I think you're rationalizing yourself into a weird situation here. But you're not too far off a valuable track.
Yes, being stealthy isn't free - particularly in combat rounds where you are charged the hide action for the privilege of being able to make a stealth roll to avoid being detected by enemy combatants because, in effect, it slows down what you can do. Fail to pay that charge and you don't get the benefit of sneaking around by using your stealth check to beat their perception check (passive or otherwise). But that's just combat. If you're not in combat, you don't need to worry about religiously paying for actions. The overhead of moving around and doing things more carefully doesn't need to be so carefully accounted for.
The beauty of being a rogue able to take a hide action as a bonus action is they are a lot more efficient with their sneaking than non-rogues in combat. They can get as much done as a non-rogue and still use their stealth check to try to avoid detection. But outside of combat, you don't need to worry about their improved stealthy action economy.
So it's OK if Bob the warlock is sneaking around trying to find a secret door in a potentially compromising location. You're not worrying about combat actions. Just have him roll his stealth check and, if he's got a better result than the guard's perception check, he finishes his search undetected. If he fails, the guard hears him poking around (even if he can't see him). If the guard reacts with hostility and it's pertinent to roll initiative, then Bob is well advised to hide to get another attempt at a stealth check if he wants to diffuse the situation. And that's gonna slow him down. Whereas if Sneaky Goyle was in that situation, he wouldn't be slowed down.