RewriteRule code in the same website. Once you have used
RewriteRule for any of your rules, you must use it for all of your Rules.
RewriteRule ^thispage http://www.example.com/thatpage [R=301,L]
is functionally no different to
Redirect 301 /thispage http://www.example.com/thatpage
RewriteRule gives you more control because
Redirect automatically re-appends the rest of the original path on to the end of the new URL.
Mixing the two types of directives in one site can cause many issues. Stick with using
RewriteRule for both external redirects and internal rewrites.