With the Pen-F and its incredibly good 5-axis IBIS, it is recommended to always use IBIS, except when that is not possible.
One of those exceptions is OIS that cannot be switched off, f.e. with a Panasonic Lumix 42.5 F/1.7 lens. In that case, do switch off IBIS, and set preference to OIS. The reason for this is that Panasonic OIS and Olympus OIS do not work well together - they fight each other; I know from experience.
With 3rd party lenses, if they are not recognized by the body, or better, if the FL is not recognized by the body, you have the option to use OIS if the lens has OIS, or alternatively use IBIS, ideally with the FL dialled in. However the in-body lens-database only has 10 entries, so one tends to run out fairly quickly. If this non-recognised lens is a zoomlens, you'd need to dial in each FL when using it - this is a bit of a pain. I haven't encountered this personally yet, but it is recommended nonetheless.
Next there are adapted lenses. Some adapters and speedboosters do recognise specific lenses, and in that case it is up to you to use OIS if the lens has it, or switch it off and let IBIS do its work. The latter is better, based on my own experience, f.e., with the Canon EF 100-400 L IS II and a Metabones adapter. If it isn;t recognized, and th elens has OIS, it is easiest to use OIS; alternatively, do dial in the lens FL and use IBIS (or use IBIS anyway ).
BTW, I do get about 6 to 7 stops of IS out of IBIS with any adapted lens without even trying, and more when I really try. However, my hands tend to be rather steady. That is shooting an adapted Canon 135L (Metabones 0.71x Speedbooster, results in ~ 100 mm lens or 200 mm FF equivalent) at 1/2 second to 1 second. Back when I had the 100-400L IS (first version), I shot it up to about 1/40 handheld on APS-C at 400 mm without a problem, which is about 2-3 stops over the official IS limit of 2 stops.
In short, don't worry about the FL and using IBIS. It will always work well, except with lenses where you cannot switch off OIS if it is known the two don't work well together (like the Panny 42.5 F/1.7 mentioned earlier).
HTH, kind regards, Wim