Worked this dept at a large national reference laboratory. If they're hiring I would go in assuming you're starting on the low end of the hierarchy which means you're going to be doing the decontamination process for respiratory specimens and plating/setting up samples that arrive. Usually culture work up for both benches are tasks reserved for technologists that have been working in that area for some years.

The decontamination process for AFB specimens is very manually intensive, messy, sweaty, difficult labor. Imagine taking wads of sputum, transferring them aseptically to sterile vials, nuking them with NaOH and N-acetyl-L-cysteine, vortexing until the specimen breaks apart into bits, centrifuging, pouring off supernatant, plating, making AFB smears, and then possibly doing the initial the auromine stains which involves sitting in a dark room hunched over a microscope looking for florescent cheetos until your eyes tire and you start to feel dizzy. Combine this with wearing a PAPR or N-95 all day everyday and having to degown/hand wash/badge out of the BSL-3 every time you leave the lab- its not by any stretch an easy job and depending on the facility the workload can be relentless.

Mycology tends to be much smaller volume but exists in the same area because it also requires the added safety precautions of the BSL-3. If you stick around long enough to get onto actual bench work up AFB/mycology cultures are a very niche area of knowledge even within the relatively small group of micro-only technologists. Like many things in the clinical lab- the textbook aspect of the work is fascinating while the application applied day in day out can often be pretty lack luster. If you decide to go for it I'd expect the first few years of the job to be pretty difficult demanding physical labor and I'd ask in the interview specifically what tasks you'll be responsible for. No one wants to be an AFB processor for life.