Leather conditioner is not used frequently. Leather dries up and needs to be conditioned every so often. Too much conditioning is a bad thing on leather, so only do it when you need to. Frequency depends on the usage it receives. Same goes for boots, jackets, etc... However, leather needs to be 100% clean before conditioning for best results. That way it goes into the pores.
Interior detailer is a maintenance type of spray. You can use it more frequently to clean up light dust or just refreshen up your interior. They both contain UV protection and if im not mistaken they both equal spf 65 protection. Whenever your leathers are visibly soiled, hit it with the stronger leather and interior cleaner first.
I personally use interior cleaner first only if the interior is very dirty or you can see dirt spots. Then I follow up with leather conditioner only if the leather needs it or its been a long time. After that im done. Just keep maintaining it with interior detailer after a few days to wipe off the dust and provide additional protection.
If the interior is already clean and doesnt need conditioning, i just give it a pass with interior detailer and im done.
For titanium coating, id just stick to cleaning them and avoiding the polish. I used to be on a forum where a guy polished his titanium exhaust, but didnt know it was coated only. He ended up getting a stainless steel mirror finish and got rid of the titanium coating. I forgot what he used tho, but id stay away from it. It was for a motorcycle, but same concept
Chonke's post in Interior Detailer Questions was marked as the answer