hello, I've been using RB951G-2HnD in dual wan failover since 2014 when I set it up myself.
It's been working ok, just 1 problem: port1 is dropping to 10mbps mode from 100mbps. I have to manually disable/enable it once a week, that's annoying. Now I'm considering to upgrade it to some newer model, are there any under $100?

I need:
5 ports 1gbps
wifi
failover + load balance possibility
also planning to add a 3rd ISP in LTE for power outage situations.

have you try to upgrade to latest ROS version and firmware? maybe netinstall the device?
why dont you use another port instead of port1 ?
hap ac2 i think is what you need.
maybe rb750gr3 or RB760iGS combine with hap lite for wifi is good to go.

I have all 5 ports used:
port1 ISP1
port2 ISP2
port3 PC1
port4 PC2
port5 PC3

so no point in changing ports. Just updated the firmware from 3.12 to 6.42.2, maybe that solves my problem for now.
In hap ac2 it says 4 core 716 MHz cpu (IPQ-4018), but is it faster than 1 core 600MHz in RB951G-2HnD?

The IPQ4018 used in new products is much faster than the CPU in RB951G-2HnD.