Bunch vs Breakaway Efforts A Quick Look
Looking at a two man breakaway, you would likely see an average power around their aerobic threshold (2mmol level or L2 for Fitlab zones). Note this is not the higher effort of OBLA (previously referred to as Anaerobic Threshold or what people attemptto predict with FTP, but rather the point where your aerobic system starts cranking). This is probably around the 4-4.5w/kg for the pros. The hills would be kept fairy even, likely around OBLA (L4 or FTP and at least 5w/kg for the pros) or a bit higher for the shorter hills and a little lower for the longer ones. In the final 30km or so, you would likely see riders upping the pace and getting close to OBLA.
The more riders in the break will mean the laps get shorter. Think of it as the rest or non-lap part as being more important. With two riders this will likely be over a minute, but with say five it may be 20-30 seconds and with 10 it might be just rolling through in a continuous chain. The intensity of the turn on the front will be higher with more riders too and will likely be above OBLA in the bigger groups. Remember the goal is establishing the break initially, maintaining and then trying to hang on to the finish (read this very hard initially, sustainable in the middle and whatever you have left in the final).
In the bunch, where a rider is just sitting in and being sheltered, their power would be in a much bigger range e.g. long periods of very light 2-3w/kg interspersed with very intense blocks. The length of these blocks would be dictated by the course, conditions and how they race it, but plenty of short burst (e.g. over a hundred) of 5+seconds and over 10w/kg. The climbs, cross wind sections and finishing km’s will also send the riders well up into VO2max and anaerobic efforts (likely around 6w/kg and higher).
So while this is a bit of a generalisation, it should give you an idea of a typical breakaway or bunch effort. Obviously each race has it’s own variables but these are some general observations. The trick here is what physiological systems are used and how to train them to sustain these efforts.