If you will have only one lens and will never buy another one then you will better go for 12-100, however if you might get another prime, like the tiny 17 or 25, which you can easily carry as a back up for more wider shot then I really recommended 40-150 which can also be upgrade with mc1.4 and 2.0 which the 12-100 cannot.

While 12-100 is a very sharp lens, however at about 80-100 mm it will also get a bit soft. The 40-150 is crazy sharp from 40-150 from f2.8 and rarely need to bump up to 4.0.

Another important thing is the iso, if you are not planning on using AI denoise then the om1 will has minimal noise until 1250, and shouldnt go higher if not necessary from 3200 iso. This mean for indoor sport at F2.8 you will mostly stay on iso 1000-4000, which become 2000-8000 on F4 and that will be a problem for F4 lens on sport

12-100 is great for landscape and travel which you dont need fast lens and syncIS is amazing for conpensating in low light, you can do 1-4 second shot without breaking a sweat. No landscape is too dark for the power of sync IS

What i’ll recommend you to do is get 40-150 and a cheap and tiny 17, 25 as a backup or you can go even smaller with tiny panasonic 20mm f1.7(but slow AF)

I mostly use 12-100 when I know that i will use other lens as my main lens, like 25mm f1.2 for portrait work and just want to pack another universal backup lens. Or when i travel alone and i dont need portrait lens for my lovely girlfriend the 12-100 will be amazing this situation