Ignore the trapdoor ram and go straight for a board with real fast RAM on it I'd highly recommend the ACA500plus from Individual Computers because of the number of features present and should cover most of your initial needs.
The card has 8MB fast RAM and a MC68HC000 running at 14Mhz, which is overclockable to 21, 28 or 42Mhz, although IC do not guarantee that the CPU will work at speeds above 14Mhz.
Kickstart 1.2, 1.3 and 3.1, and the complete install disks for OS3.1 are included on the card's 8MB flash ROM. No need for a ROM switcher and you can select to the A500 in a variety of different configurations. from the cards own menu screen.
It has two CF cards, one of which is hot swap-able, so ideal for transferring files between different systems. The card slots are pretty fast by Amiga standards too.
The card offers some extra expandability too, with a connector for A1200 clockport style devices if you can find them, a connector for IC's own XSurf500 Ethernet card and A1200 style edge connector so if you need a faster CPU and more RAM you can plug an A1200 accelerator into the ACA500Plus. Adding A1200 cards may require a beefier PSU.
https://icomp.de/shop-icomp/en/shop/product/ACA500plus.htmlACE2b might to worth looking at if you ever find yourself running out of chip RAM. It's very expensive so I'd only recommend it if you find that you have real use case for it.
https://icomp.de/shop-icomp/en/shop/product/ace2.html
