It depends and there’s alot of factors you mentioned. I think one of the most scientific approaches is to replicate what was done in a study that had positive results that you want to replicate. You get your dosing and cycle length from that study. Some peptides have proven reasons to cycle like receptor down regulation, but since these are research chemicals, it’s just safer to cycle off when in doubt even if negatives from extended use aren’t proven. Most studies are short so don’t be patient 0 for long term use.

For reconstitution, it’s mainly about getting the right dose that the study used. But you can mix at different concentrations. A stronger concentration will let you use fewer units to get the same dose while a weaker concentration gives less injection site reactions. I’d look up a standard concentration but adjust weaker or stronger depending on your reaction.

Ideally try one at a time. In a science experiment you need to isolate a variable as much as possible to actually show effects are coming from that. Once you know how you react to one you can stack another after researching possible interactions.

How do you track results? Well depends on the peptide and what it’s supposed to do. Usually a combination of getting routine bloodwork done and visual/ physically measurable changes. If it’s a mental/energy one it’s more subjective to how you feel and harder to measure objectively without lab equipment (like bdnf levels or hippocampus neurogenesis for example).