imo the answer is "whatever works best for you". IOC controls (home-lock and course-lock) change how the sticks operate and indeed lock in a certain course, I think of them kind of like cruise control... no it doesn't lock forward movement like cruise control but it locks in a certain axis of movement so you don't have to concentrate on it... which is sort of what cruise control in a car does.
Anyway if you're good enough to get the shots you want without IOC then just do that. Not sure why you're mentioning LOS... I mean you need to basically maintain LOS to the quad at ALL times so that your FPV and RC don't lose signal... so you can't go flying behind buildings or other solid obstacles... so LOS is really irrelevant to IOC and if you use IOC when filming.
If you're going to be concentrating really hard on your FPV screen trying to get fancy camera shots, it's best to have a spotter working with you making sure you don't move into an obstacle accidentally. much easier to have a spotter than for you alone to be looking back and forth between the FPV, quad, FPV quad
Obviously if you're trying to get a certain shot you use the FPV to see exactly what the camera is seeing... so if you're looking at the FPV screen with IOC off all the controls are "normal" .. left is left, right is right, forward is forward, etc. so I personally never use IOC, I just get the shots I want manually with normal stick control.
Some people say it's easier to get certain types of shots with IOC, so you can concentrate on camera/gimbal and certain axis movements and not have to manage everything yourself, but so far I've never wanted to get a shot and NOT been able to with normal stick control...