A lot of that is personal preferences. I have a CRS326 that is being used exclusively as a managed switch. Other than about a half dozen VLANs, there is nothing fancy. I am running it under SwitchOS and always have. I also have two CSS326 switches - obviously running SwitchOS, plus two a CSS106-5G-1S and a RB260GS. My switches are used exclusively as switches and use SwitchOS. My routers are used exclusively as routers and use RouterOS.
Based on your needs, I would use RouterOS as you are trying to do things that SwitchOS does not support.
BTW, in case you are wondering why I bought a more expensive CRS326 rather than another CSS326 - I didn’t. The vendor inadvertently shipped me a CRS326 when I ordered a CSS326. When I realized the error, I contacted them and they decided it was not worth the time nor expense to ship me a CSS326 and have me ship the CRS326 back to them, and told me to keep the CRS326. Not only that, but for my trouble, they gave me an account credit to be used on a future order. That’s what I call customer service. And yes, I have bought several more items from them - and will continue to do so in the future.