Tools
Remus and romsplit - these are tools for use on the Amiga http://www.doobreynet.co.uk/beta/index.html
Capitoline - Kickstart editor for use on Windows http://capitoline.twocatsblack.com/
ROMY tools for creating 1MB/2MB ROM images https://github.com/reinauer/amiga-romy/tree/main/software
EPROMS
The standard size for the A1200 would be a 2x AM27C200 (256KB) however these are not readily available - AM27C400 which are 512KB each are more readily available. This is an EPROM that instead of the standard JEDEC EPROM pinout has one suitable for replacing a mask rom. Ideally 100ns speed or faster (although I see some people saying 120ns is OK). I got the -105 variant.
The original Kickstart ROM will only occupy 512KB - so using the above mentioned tools you could make a custom image and incorporate other libraries, e.g. workbench.library that has been omitted from Kickstart 3.2 ROMs or a driver such as ehide, as needed by the Terriblefire TF1260 and TF1230 IDE adapters.
Adapter for the TL866
These cannot be programmed by the TL866 without an adapter. The one I have is https://github.com/gaggi/27c160-tl866-adapter which appears to have been forked by https://github.com/mafe72/27c160-tl866-adapter and the manual translated into English.
When using the adapter, select AM27C4096.
Flash
GGLabs F2R16 https://gglabs.us/node/2067
USB 27C400 EPROM Emulator http://www.boobip.com/hardware/27C400_EMU - this is not available due to component unavailability
Open hardware flash adapters https://github.com/OlegMishin/FlashROM