@Pampa
If you're having serious differences in your fitness (CTL), fatigue (ATL), and form (TSB) metrics, I would double-check to make sure you have an accurate FTP input in both Strava and Intervals (These are manual inputs). Data is calculated off of your FTP, so any inaccuracies will output skewed data. I never use Strava metrics, but I just checked and they correlated quite closely to Intervals. My most accurate performance metrics come from the TP/WKO platform as my historical FTPs are recorded there and therefore subsequent workouts are calculated according to those numbers. For reference, my TP CTL is about 10 points higher than Strava/Intervals.
I prefer Intervals.icu over TP premium for a quick metric scan due to intervals superior power duration curve model. I use TP for training planning, workout creation, and sending workouts to Zwift or to my wahoo for structured outdoors work. I ultimately use WKO5 for the heavier data geek stuff and am still learning how to get the most out of this monster piece of software. I will be using it for custom workout creation according to my power profile this season. Golden Cheetah is a wonderful free open source alternative, with a feature set out of this world. The difference is that they are built around the Critical Power model vs WKO/TP FTP model, which will give you essentially very similar data. I think they were planning on allowing the use of FTP as well, unsure whether this was implemented or not. Haven't used GC in over a year. GC is certainly worth a look to play around with if you want to mess around with and learn some metrics. I jumped on WKO when they had a nice sale going, 30-50% off, I don't recall and suggested to my wife that it be her fathers day gift to me