Hello, i need better understand how to set dual WAN the correct way

Currently i have most basic setup - pppoe in port 1 made by quick set, router mode + i added 4 wireguards (and firewall rules). ISP1 provide static public IPv4 + static IPv6 /56, speed 120/25Mb. Everything work fine.

Because ISP1 cannot provide more speed i bought 5G 250/25Mb as second connection. ISP2 provide CGNAT + single dynamic /64 (routerOS lack ND-proxy IPv6 is out of question)

Main reason for this is offset heavy usage streaming videos on TVs (UHD in 60fps) and phones.

What i tried:
1) Client IP load balancing - Based on this video: https://www.youtube.com/watch?v=oRu03tdOrak a manage it to work (video is based on ROS6) but all wireaguards and LAN was not accessible (Winbox was accessible only by MAC address), later i managed to LAN work but Wireguard was never resolved, also IPv6 was assuming control sometimes so i have ISP2 IPv4 but ISP1 IPv6, it was not reliable to work with so it was scratched

2) PCC - Based on this video https://www.youtube.com/watch?v=nlb7XAv57tw it was half working solution but some pages started behave strange (they were load, then blind to later been loaded again), it had also problems with banking apps on phones so i scratch that too

3) EOIP - I tried EOIP two routers but i cannot make it work but based on forums it is promising to interconnect networks

4) Two LANs, Two Bridges - basically one physical router behaving as two virtual. Before i start i need to ask if this is even good idea.
I basically want - port 1 as WAN1, port 2-4 bridge1 ,, port 5 as WAN2, port 6-8 Bridge2 then i physically will switch cables, not desired but i can utilise power of one device and later try EOIP the two bridges. It is even reasonable or it will have unforeseen consequences?


Current setup until i resolve this

ISP1 -- Modem (bridge mode) > RB5009 > devices as PC, NAS, Consoles (preventing NAT problems), Main access point
ISP2 -- ODU (5G modem) > Hex S > Switch > devices as secondary access point, TVs, phones
Both routers are interconnect with wireguard

What is desired - Use one physical infrastructure but move heavy traffic to ISP2
That will be the best solution but other reliable solutions will be also welcomed.

sorry not familiar with ipv6 so cannot assist.

Bigleaf device sitting in front of your network.

Put both ISPs into that box.

It will give you one PUBLIC IP ADDRESS.

It will handle seamless failover and run on the fastest feed available unless you tell it to do other wise.

Yes it has a monthly fee.

epilogue:
Bigleaf was so overkill, I decided to go back to basics.
I connected both routers in failover + added a couple of routes to reach the desired devices from both networks, then I will add more UTP cables to physically separate networks for the two new APs for good 5Ghz coverage and a quick change to the desired network (WAN1 - ethernet for console NAT problems with games stability, WAN2 - for fast downloads via Wi-Fi). Easy to maintain, not that expensive, extra fast switching and they work as intended. No more complicated dualwan settings.

If they provide 500Mbs on 5G in the future I will ditch DSL altogether and just buy a static public IP and migrate all the wireguards.

epilogue:
Bigleaf was so overkill, I decided to go back to basics.

Glad you found something that works for you.

Here is the only thing...

I object to the word OVERKILL.

I think its a little more accurate to say "Here are the inherent flaws I am willing to accept."

Because here is my take on the matter... I mostly work in commercial where downtime or flaws result in the loss of revenue. So I tend to look at things like this "WHAT DOES IT COST WHEN IT'S NOT WORKING?"

Between internet delivered audio and video and real time things like voice... having a connection get "shakey" or fail then wait for detection and reinitiation of connections can be "Who Cares?" to "F--king YouTubeTV signed all my TVS out and required me to reenter credentials on each one!!!"

So I tend to base things on, "how annoyed are they willing to be."

"I was on a call... the call dropped. I tried to call back and it didn't go through the first couple of times. Once it did establish we got back into the conversation when the call dropped again. I could call right back and it was fine."

Or when a connection makes the call unintelligible for an extended amount of time because the connection to the VoIP gateway from the ISP is the issue. But since the call is ongoing... you have to hang up and wait for the main feed to drop or cut it off manually to get the call to go over the backup.

Its just I don't wanna hear about it... the customer doesn't wanna know about it... they want it to "JUST WORK". (Notice that's 2 four letter words right next to each other. F--K S--T as an example.)

So I won't even talk to clinets about rollover anymore as it always results in the "I thought it would be SEAMLESS!"

I don't like having to make excuses before we even start... so I gave up on my recursive routes I have used for years.