Doesn't matter which way the goal is avoid sleeping on the plane/flight if at all possible (I avoid alcohol), and if you must sleep align it with the destination time zone. Think of it as the morning you wake up change all your watched and personal devices to PST time zone.
IMO, 13:55 departure is 5am LAX time which is simply a long day if you can stay awake the entire journey as adjust proper.
If you leave early AM with connection - you are shortening yourself sleep in PST/LAX time resulting in naturally wanted to get to bed earlier - which hurts your time. If you left 8:00 UK you are 12am LAX/PST which incorporate breakfast and other noise disruptions even if you attempted to sleep as soon as you get into your seat you are awaken for connection and going to arrive tired.
Each person handles differently so only my experiences. The unknown is when you land LAX are you still working remote/mobile UK or EST or local time? As that factors into the equation. I find the 2nd day is the hardest as one can use caffeine to balance out the first 24 hrs but 25+ is hard crash especially if don't allow natural adjustment/sleep patterns.