If you don’t get much traction here on your question, it might also be worth asking the Apple Collectors forum. Much of the activity on this forum tends to bias toward G3-and-later systems running OS 8.6 and later.
I still use my venerable 7600. For a display, I generally use an old Apple Studio Display with an ADC-to-DVI adapter, but I can only do that because I have a video card installed with DVI (a Radeon 9200). If you're using the onboard DB-15 video, you would need either an Apple CRT from that era, or any display with VGA if you also have an adapter for VGA to DB-15. It may be hard to get ahold of CRTs in good working order these days, if you don't already have one. But some early LCD displays had VGA ports, so that could also work.
I don't have any experience with adding Wi-Fi via PCI directly, but in the past, I did use a USB Wi-Fi module connected to a USB card in the 7600. It was theoretically a little faster than the onboard Ethernet, but generally I just use the wired Ethernet to keep things simple.