Dot not underestimate the ram size of a router, bigger ram size will definitely result in better capabilities to handle higher network traffic, the benefit of bigger ram is more obvious when there are more devices connected to the network and torrenting. Not to mention, AX55 does not have Merlin support at the moment. Based on the specification, it seems there are also some missing features in comparison to AX-56U. The price difference between the 2 is not obvious, i strongly recommend you to get AX-56U, I’ve been using this router close to 1 year, 0 regret, insanely huge improvement from the shitty Maxis and Unifi Router, and it’s getting better with the release of every new firmware update.

I get your point there mate. Sometimes, I do wonder why ASUS cramp so much unwanted feature in their entry level routers (which won't be fully utilized by common users). On the other hand, for power users under a tight budget, this will be a good option for them to fully utilize the router. Regarding the auto <thing>, most router coded like that these days. In other word, setup your PPPoE credentials, your wireless SSIDs and router login credentials, then you're good to go.

Secondly, Archer AX20 surprisingly a good router. Heck even better than the AX56U in terms of wireless performance. Additionally, it does have a standard features, not too advance and not too basic. Archer AX20's settings seemed simple due to the execution of its user-interface and correctly mapped main button for the feature access (talking about visual pleasing experience). For my personal usage, I only use ASUS (for consumer grade router) or Mikrotik for enterprise (if needed in the future).

budget wise and short term usage = ax20 > ax56.
performance and long term support = ax56 > ax20.

In the end you should decide which is suitable for your use case. If i were you, i will save some cash to opt ax56u than ax20.

Unfortunately I don't test the router yet mate. So I can't give my personal opinion on the ax73. Kindly check other blogger's review before settling down with a right unit which, you prefer suit you and your pocket.

You won't regret getting AX73. It's good for 2 storey house without having to install mesh. Strong signal & good coverage.