OR get the bundle with NExT WITH free Shipping…
If you have access to a 3D printer, there are some files here to do just that
There are different opinions on this, some as you suggest, some doing them all in the same sitting ( That is MY preference) one period of healing rather than dragged out, but I also get the logic the other way )
Putting it simply, (Trying to answer in a simple but non-condescending manor)
if we take your NExT for example it has two chips.
HIGH FREQUENCY
13.56MHz HF that uses NFC protocol to talk to and write NDEF records ( your business card details ) which is stored on the onboard memory 888 bytes. The chip has a 7 byte UID which it uses to an enrolled access system. This UID you cannot change.
LOW FREQUENCY
125kHz LF that has and uses a changable UID also changeable modes, EM/HID/Indala etc but doesn’t store data like the HF chip above
You can enroll your LF chip into compatible readers, if you can’t enroll it, you can clone the original card / fob with a suitable reader / writer ( proxmark / blue cloner ).
Does that answer your question?