You'll really want to print most things, except;
Superceded_parts, skip.
Bowden, skip.
Test_Prints, skip.
Skip any parts that deal with the stock, small front display, (mini12864) you'll be using the BTT HDMI 5" from the kit and those are in the Formbot files.
You only need the correct bracket for your BTT Manta, none of the other ones in the package. Manta is a brand new upgrade for the Formbot kit, so the Octopus bracket may or may not fit, check the hole dimensions before printing.
You'll use Voron TAP for Z-offset, homing, quad gantry level, making a bed mesh and so on. So none of the probe mounts, brackets or retainers are needed.
The kit has generic cable chains, only chain anchors for 3 hole chains is needed.
Only the printhead that fits your specific hotend is needed, none of the others.
An ADXL345 can be mounted directly to the hotend assembly, this is mentioned in the manual, so you can skip the ADXL345 files.
The PSU only needs the "lrs_200" psu bracket, the PSU_stabilizer will not fit if the electronics are turned 90 degrees.
RS25_psu bracket is not used. Wago mounts are not used.
Anything to do with "hall effect" for endstops is not used, skip those files. You have physical limit switches for X and Y.
Skip the whole "X_carriage" folder since the Voron TAP files replace everything in there.
Skirts are all optional, but I recommend them, to keep fingers out of the electronics compartment but they also add that much needed PIZZAZZ 😛 Oh and some of the skirts hold the cooling fans for the electronics, just print them all!
The skirt that holds the filtered power inlet is not optional however. Skip the other types of power inlets.
Skip any skirt folders that aren't for your model, obviously.
Nozzle probe, skip.
There are two doors for the print head, one has "pcb" in the name, pick that one.