I don’t have access to the lulz’ hex hot ends any more than you do. I am just a Taz owner like you but I started with a Taz 5. I have since purchased an extra extruder (with hex), a couple half height steppers and a flexi-dualie. I had to clean the nozzle on my dualie and I can’t get the nozzle back on, threads were stripp3ed when I removed the nozzle. So thats a piece of trash at this point and I am not very happy about it.
Lulz isn’t stocking the Hex in their store for some reason, I am guessing its production is dedicated to supplying new Taz5 sales. I can’t get them either for developing a dual extruder with all metal hot ends. For that reason, I will likely be going with the E3D V6 for the dualie designs I am working on.
And if you are starting with a Taz 4 with a budda hot end, yes, you will need to update your firmware if you change to an all metal hot end like the Hex or E3D. The budda uses a different thermistor and heater than the E3D and Hex. I don’t think and E3D/Hex will heat properly with the firmware from the budda (lower power settings for the heater) though I have not tried it first hand. By contrast, you will toast a budda’s heater if you plug it into a taz with a firmware set up for a hex. The E3D and Hex can and do use 3x the power that the budda does.
That said, changing the firmware isn’t that hard. You just need to edit a few settings in one file and then upload it to your Taz. Its only a few minutes of tinkering. I have firmware saved for the Hex and a 2nd copy for the Budda. That way all I need to do is load up the proper one and upload it to the Taz when I change heads.