Hey there.
Disclaimer:
I'm not writing this as a tutorial or a how to but only as an "article regarding the topic in general" :D.
That's pretty close to what I do at home.
Just recently I got myself a BananaPi M1, which is available for ~50€ (board + case + power cord + micro-sd card).
On this BananaPi I created an interface on eth0.2 for WAN, a second interface eth0.1 for LAN and a couple of other interfaces on different VIDs for other vlans.
I run 5 regular SoHo routers (TP-Link 4900, 4300 and 1043) "daisy chained". They do not provide routing but only act als "dumb AP" and managed switches.
This section is what the following sections have in common.
My actual setup:
Router1 uses its WAN port as "VID2 untagged" to connect to the CAT5e port of my ISP.
Router1 uses its LAN1 port as "all VIDs tagged" to connect to the BnaanaPi.
Router1 uses its LAN2 port as "all VIDs tagged" to connect to Router2.
Router1 uses its LAN3 and LAN4 ports as "VID1 untagged".
Router2 uses its WAN port as "all VIDs tagged" to connect to Router1.
Router2 uses its LAN1 port as "all VIDs tagged" to connect to Router3.
Router2 uses its ports LAN2, LAN3 and LAN4 as "VID1 untagged".
Router3 through Router5 are configured in the same way Router2 is configured.
Router6 uses its WAN port as "all VIDs tagged" to connect to Router5.
Router6 uses all its LAN ports as "VID1 untagged".
There's 4 additional managed switches around here that are configured just like Router2 through Router3 with one in and one out tagged port and a couple of untagged outlets. That makes nearly 30 individual rj45 ports around the house that serve VID1 by default but can be adjusted to other VIDs, like guest, DMZ, IoT or my brother.
The setup you are aiming for:
You should configure all WAN ports of your routers to "all VIDs tagged".
You should configure all LAN ports of your routers to "VID1 untagged".
Your should decide a single port of your HP switch to connect "all VIDs tagged" per router, preferably the GBIt ports.
If your ISP only provides you with 75MBit, I wouldn't make one of the GBIt ports of the HP switch the WAN uplink to your ISP. Just use one of its 100MBit ports as "VID2 untagged" and save the GBIt ports for WiFi.
This allows for max performance between WiFi clients even if they are on different routers.
Other hardware
As we all know, more is always better :).
If you decide for more GBit ports on your LAN, I'd suggest something like the D-Link DGS-1100. It's available for between 30€ (8 port) and 110€ (24 port).
What I should have done
Of course, my daisy chain strategy relates to not having properly planed my home network in the first place.
The way better solution would be a single core managed switch that powers the house entirely, providing 5 ports for my APs and additional 43 ports (since a 32 port device won't do I'd go for a 48 port device) patched to different rj45 outlets around the house. This setting would completely ignore all rj45 outlets of the APs since all connection should go through the core switch.
The next best way would be a single smaller switch 16 port switch that connects all my APs and managed switches. This dramatically reduces the number of wires I'd need to drill through walls and floors (from 32 down to 16 at most).
On to of that, if the "core" switch only connects a couple of VLAN aware distribution boxes (either 5port SoHo routers or cheap 8port managed switches), the "core" switch itself doesn't need to know anything about vlans. Which, in turn, saves some bugs.
Regards,
Stephan.