all these while i've only used varchar for any string

i heard from my ex-boss that char s speed up searches. is that
true?

so there are these:

1) char with index
2) char without index
3) char with clustered index
4) varchar with index
5) varchar without index
6) varchar with clustered index

some of my tables primary key (clustered) is a string type. would it
be benificial to use char? or would using (6) makes no difference?

for non primary key columns that needs to be searched a lot, can i say
(1) is the best?