Mwan3: Router for combining 5G Phone Hotspot with VDSL connection

Hi,

I have a 5G unlimited data sim card in my phone and a VDSL connection. I want to combine them to get faster internet speeds, when I’m at home, otherwise use VDSL.
I have tested mwan3 with an old openwrt router and it works great (Kudos to the authors), this is what I need! However, the old openwrt router dir-825 has poor wifi performance.

At home, I can measure the following:
5G Phone Hotspot ==802.11AX==> laptop = 150Mbit/s
VDSL modem ==802.11AC==> laptop = 60Mbit/s
VDSL modem ==GBE==> laptop = 60Mbit/s

If I only use cable, no wifi, then it works great:
5G Phone USB Tethering + VDSL modem GBE ==> old openwrt router dir-825 with mwan3 ==GBE==> laptop = 200Mbit/s

With 802.11n wifi, but with usb tethering it doesn’t work great:
5G Phone USB Tethering + VDSL modem GBE ==> old openwrt router dir-825 with mwan3 ==802.11n==> laptop = 50Mbit/s

Now, this is the configuration that I want to have, but 10x faster:
5G Phone 802.11N Hotspot + VDSL modem GBE ==> old openwrt router dir-825 with mwan3 ==802.11n==> laptop = 20Mbit/s

I’m thinking of buying a belkin rt3200 802.11ax router that has the MediaTek MT7915E modem on 5Ghz.

So my questions:
-Is it possible to have with MediaTek MT7915E (that is inside belkin rt3200) a wifi client and AP on 5Ghz at the same time? (Not as a simple repeater, but as separated VLANs for mwan3)
-Should I rather choose a router with 2x 802.11AC or AX modems? Can you recommend one that is below 100 Euros?

Thank you!