Once you get the other cell monitors in place, this info becomes lots less important.
The discharge curve of an LFP cell has a pretty steep voltage drop around 2.8v indicating an empty cell. (dont change your 3v minimum bms setting unless all cells are monitored).
Bottom balancing refers to equalizing all cells to reach this (empty drop off ) at the same time.
Your cells are new and likely to have very similar capacities, therefore the upper voltage knee for full charge will occur at the same time for each cell as well as the lower knee will happen at the same time for all cells when they are balanced. But lets assume they are getting along in years and capacities vary by 5-10AH. This would mean you could align the discharge knees of all cells to reach empty at the same time and when you charged them one with lower capacitiy would reach full and climb past 4.0v while the others are still reading high 3.3s. If you want an LFP to last avoid going below 3.0v or above 3.5v theres really not much capacity to gain on either end. Ross likely can improve on these numbers.
The bottom balancing trick comes from the EV guys who became frustrated with the poor reliability of the early BMS systems and in some cases decided they were better off without. (kind of like an oil pressure guage that leaks and causes your engine to run out of oil). If you get rid of the BMS the best way to protect your LFP cells is to meticulously align every cell at the lower knee on discharge and monitor the pack voltage for your fuel guage. EV fellas are trying to get the best range possible sometimes at the expense of the cell. Your application can be more conservative with the min and max points and treat the cell better.
Regarding bolting the cells together, Nope, i would not do for balancing. The current exchange without resistance could be damaging. If you want a simple way to balance manually then choose a low voltage 6v halogen lamp of 100w or whatever is handy. Then you can connect neg to neg and positives together through the lamp. Use something available and cheap, any low resistance filament or resistor will do. Once two cells have equalized with low resistance then you can bolt together if building a pack etc.
Those prismatic cells though expensive are the closest thing ive ever seen to an ideal (textbook) battery. For all practical purposes of realistic calculations you can even skip the symbolic internal resistance. Do try to cover/insulate those terminals and fuse where strings join. Lead acids can source huge current but LFP can produce current beyond anything you can imagine. Unless there is protection there may not be a tomorrow. Cant say ive seen one shorted but ive seen 4kw from a pack the size of 2 car batteries without much v sag.
Unless external equipment unbalances your cells, they dont need much balancing but monitoring is a necessity.
Good to see the progress, i feel your pain with the variable unexpected loads throughout day and night
imagine trying to manage the Grid.