In the 50? My weakness was that I never could kick, so I always recommend kicking. Legs won't burn out in a 50. Also head down, breathing is overrated.
In the 100? I'm sure you've heard this a million times but that first 25 should be easy speed/let the adrenaline carry you. Make yourself do a few underwaters off each wall and build that second 25 and then hit that last 50 hard. Good warmup, stay loose, stay awake
caveats -- my best time in each event was like a 22.2 and a 48.4 and that was like when I was 18 so in the very real likelihood you've outpaced me already take this all for the little its worth