Orally. The non-water soluble benzos (ie most of them except midazolam and a couple of rarer ones) are poorly absorbed intranasally. Insufflating pills isn't good for you either - lots of fillers/binders/crap coating your mucous membranes and filling your sinuses, and even entering your lungs. Some opioid pills have a higher intranasal bioavailability but it is not a universal rule (oxycodone and morphine have a higher oral bioavailability for example) and clonazepam is certainly better eaten or taken sublingually..
If you want fast onset then sublingual is your best bet.
There is no "max dose" of benzos when on Suboxone - it very much depends on your individual tolerance. Combining opioids and benzos can be dangerous so it is important to be careful. If you have no benzo tolerance then you shouldn't take more than 0.5mg clonazepam really..
Is the clonazepam prescribed? If you are taking it to treat panic attacks then I recommend speaking to your doctor - a long-lasting benzo like that isn't necessarily the best choice for panic disorder, and they can advise you on what dose to take.
