Are IOT wireless network protocol right for high throughput point to point communication?
This chip meets all your requirements:
https://www.semtech.com/uploads/documents/sx1238.pdf

Throughput: You would like 600 bytes/sec broadcasts?.. this chip can do 30,000 bytes/sec, so that should be more than enough

Latency: Since it is a raw modem chip, the latency is just the over-the-air modulation period. At 300kbps, that is ~33 micro-seconds per 1 byte (or 0.2ms per packet).

Network: Since it is a raw modem, you can broadcast to infinite chips. Either make your own protocol, or if you are bad at software, I would just use 2 different chips (1 for RX and 1 for TX, on different frequencies). Each RX + TX pair that has its own frequency pair is a private link, so can make hundreds of "private links" if you want to.

Professional chipset: Yes this is a "professional" chipset. Semtech is a very reputable company with very good support. You should email/meet with their FAEs.

If 2.4GHz is ever an option: I would just use an esp32 (which has custom protocols too, not just wifi). It will just work out of the box. Not sure why you need +27dBm, but LR mode has a large link budget.