You're only supposed use one extension (about 3'). I have used a HT131 or whatever the big boy is. Its way heavy and limited use for me. I rarely use a pole chainsaw.
I think I've seen a video of three extensions plus the pole saw shaft/ gearbox bar making about 20' or reach.
My orchard ladders extend the reach, and allow better cuts, as its lightweight. I can about one-hand the powerhead and pole with no extension (sometimes when whacking stuff back, pulling down a branch and whacking the end off is enough for the task at hand, like sectioning back a long upward-growing limb where you need out of reach tips).
I have a blower (step up from handheld Stihl, before the BR600).
I have the brush cutter blade, string trimmer, hedge shear that I use a couple times a year (I've been working on shearing low branches around conifers that people want to be able to mow around easily, rather than canopy raising, creating problems, and losing screening. I have some hedge at home. A few in the mix at customers houses.
There is a new electric Kombi with all electric tools. Too bad the electric doesn't just spin the drive shaft on old tools.
There is a power broom that I'm considering, but its a $400 attachment IIRC, and I don't know how it will work. Probably once you have the main parts, the other wheels (bristle broom, rubber paddle broom, IDK if there is a third) would be a small add-on.
Would work for light snow, stump chips, not sure about rakings, though, which is what I really want if for. Stump chips move with a blower, to a degree, and I have 3.