we currently have a 25Mbps fiber line that will be bumped up to 50Mbps or even higher in the future depending on our growth, along with a 10Mbps line. as it stands, we also have the MikroTik RB951G-2HnD set up using bandwidth based load balancing using the 25Mbps line until ~20Mbps saturation before shifting over to the 10Mbps line. what I’m wondering is if there are other solutions to better utilize both lines, specifically PCC, if the 25Mbps will likely increase in the near future.
I 'd say there’s no better approach per se, that will depend on what you have, and what you need.
Once you have multiple uplinks, it’s up to you to decide which “mix” of load balancing, failover and policy routing will better suit your scenario.
So you have to gain knowledge of it first, you can set for example mangle rules to match different kinds of traffic, (with action accept or log without actually enabling the log tick) so that you can look at their counters periodically, to have an idea of your traffic distribution.
Alternatively, for a more precise approach, you could use IP > traffic flow to send summary data to another system for later analysis (ELK, or the like).
Once you know your network traffic patterns, you will be in a position to make an informed decision about the better design or decide what is the best approach.
e.g. does 10Mbps line have better latency? Route DNS/VoIP traffic through it, load balance “bulk” traffic assymetrically on both, and make it failover to the 25Mbps.