I really like to remind people that BioPellets are NOT Carbon dosing.You very likely will have different bacteria grow from whatever you dose vs whatever the biopellets are. Hard to kick start and then switch.
Sugar is fine. Vinegar is fine. Vodka is fine. Biopellets are fine. A mix is fine. I hate the smell of vinegar and cheap vodka was still not cheap had too many impurities for me (although it is still probably fine)... so I went with sugar since it was cheap, pure and easy. Each has their downsides and positives. Some bio pellet reactors can get full of gunk, clog and not work right without constant cleaning, but the manufacturer and BRS videos don't tell you about this.
People used to get all bent out of shape over the particular kind of dosing, but it was all stupid... like a sticker Calvin whizzing on a Ford, Chevy or Ram truck while on another brand. Dumb. Some types have a very small chance of fueling some cyano over others, but at your levels the cyano is long since poisoned anyway... we are talking small here and not worth arguing about unless you do indeed have a Calvin ticking sticker and are a huge fanboy.
If your N is that high, then you will not likely be able to do this super slow. You will need to be somewhat aggressive while being safe and ramping SLOWLY. Most biopellet systems were made to kinda maintain and not really lower, but some can lower with larger amounts.
Carbon Dosing is a very specific practice of adding soluble Carbon to the water stream thus creating an imbalance between bacterial colonies, Nitrate, Phosphate and organic Carbon in the water stream.
Carbon Dosing creates a cycle of bloom-bust as bacterial colonies expand and then die as the temporary abundance of C stops.
BioPellets, solid Carbon pellets add NOTHING to the water. They serve as a food source AND a substrate for bacteria. Bacterial growth is limited by the available N&P in the water. Instead of feeding bacteria on every grain of sand and rock in the tank, most of the action is confined to the reactor.
Only in extreme situations will bacterial bio-mass shed off the pellets and end up covering the display.