Should I set "boost priority" to 1 or "SMP" to -1 on SQL Server?

A. No (unless the following doesn't bother you). 

Although these can offer a small performance improvement in tpcc environments (which is why Microsoft put them in the product), you run the risk of the SQL process hogging too much cpu time at the expense of NT/networking/drivers. If this happens your other SQL connections will hang or disconnect as NT won't be able to service the network packets needed to keep the sessions running.

If you do have an environment where all SQL code is known in advance, there are no ad-hoc queries, and no heavy queries, then you may get a small improvement by turning them on. But the risks aren't worth the gains in 99% of situations.