Will you have to how a property manager or are you capable of managing it yourself? 

I will be hiring and management company either way. 

I've build a decent portfolio thus far (via BRRRR) but looking to be more competitive in HCOL area and increase the velocity of my returns.

Can anyone recommend companies who manage these types of properties?

Beyond that, if you plan on your properties to be property managed, you will be paying 10% of your gross income to the property manager.  

By their calculations, I am averaging 3.5% per year from rental income for the entire portfolio.

But, managing them can be a lot of work.

On the flip side, multiple MTR/STRs in other areas could yield higher cash flow, especially in tourist-heavy or affordable markets, but managing dispersed properties can be challenging, with considerations like vacancy periods and potential property management costs if you opt out of self-management.

I also do property management for work, so I can definitely help you out as well if you are needing it fully leased.  

I recommend this book which is amount how to manage your cash.