France I believe are the strong favourites, especially with an in form Kante and Benzema coming back. The depth they have is insane.
Germany I think are also a very strong team, but it will depend on who plays. Gnabry and Sane, or Havertz and werner? The later two suit Chelsea's system but may struggle more in a 4-3-3. The lack of an out and out clinical 9 doesn't help them as werner is really better as a wide player.
England also have a lot of talent, second only to France, but Southgate will play 5-3-2 based on his squad selection and ruin any chance they have. with all the attacking talent they have, 4-3-3 would be the clear approach, instead he'll go for an extra centre back. Could line up with Grealish - Kane - Sancho/Foden, with Mount - Henderson - Rice in behind. Instead will go for something like Kane - one of the attackers, and Mount - Henderson - Rice in behind.
Portugal I think aren't as big a favourite as people think, two of their key attackers in Bruno and Ronaldo looked really tired at the end of the season. I could see them even not making it out of their group if the 3rd place finish thing goes against them.