My local ISP is installing a new fiber link to our house, they are going to use a Mikrotek RB760 - and described it as having full firewall capabilities - but I don’t see anything about that on the product description.
Does it provide firewall, and management, or will I need another device (above/Behind?) it for this?
I assume you are asking about hEX S (RB760iGS). That is a full-featured router running RouterOS. You can read more about the software here and here. It is pretty powerful and will likely cover most (if not all) your needs.
Thank you, yes - these are helpful references.
I also see that some users instead load OpenWRT - is there a comparison of issues or features somewhere?
RouterOS is enterprise-grade. OpenWRT is consumer-grade. Why would people ever want to use OpenWRT over RouterOS?
i don’t know - that was my question! 
Thanks.
Consumer, enterprise, it doesn’t mean much. And it’s not like there’s consensus about what product is what grade anyway.
RouterOS is nice and very flexible, at least when compared to many other routers. But it’s still closed system, it doesn’t have everything, so if you’re missing some feature, you’re out of luck. With OpenWRT (or other open systems) you can go as wild as you want, you can install anything, if you know how, but it’s more work. RouterOS is perfect mix, powerfull and yet simple and admin friendly (well, there are some opposing opinions about the latter :).
If you want reliable router, RouterOS is good. If you want something extra that RouterOS doesn’t offer (e.g. some things not directly related to routing, various servers, etc), you need something else and OpenWRT may be it. I’m not sure if I’d pick MikroTik hardware for it, since they provide no support for non-RouterOS systems whatsoever, but if you choose device well supported by OpenWRT, why not.
If you want plugNplay, then Mikrotik is not for you.
I am curious as to who is suggesting that there is openwrt for MT routers??
OpenWRT on Mikrotik as a MetaRouter
https://medium.com/@tomas_savenas/openwrt-on-mikrotik-as-a-metarouter-2b0bed9d62f9
Common Procedures for Mikrotik RouterBoard Products
https://openwrt.org/toh/mikrotik/common
OpenWRT - Mikrotik Devices
https://openwrt.org/toh/mikrotik/start
Google => Many more…
Metarouter is not supported on hEX S (as well as any other model with SPI flash).