My Fibre line isn't super speedy no (10/5), but its decent. The idea for me was to combine the speed of both using the load distributing router, and also have redundancy in the process so that if one is down I have the other.
Thanks for your efforts and the additional info provided by commenters. I have set mine up to have WAN1 as my uncapped fibre line and WAN2 as time based LTE from RAIN. It's working well so far. Just the initial setup was a bit of work to wrap my mind around the settings, but in the end it's...