A high training intensity workload may improve your players attributes quicker, but it will increase the chances of players picking up injuries, especially when working on physical sessions such as Fitness.
Balance between the levels of match preparation and general training depending on the time of the season. Pre-season is a perfect time to work on your tactics via match preparation and allow your players condition to increase between matches.
Resting players is key. Think about how much time you want to give them to recover; is it better suited before or after a match? During particularly tough runs, resting both days is worth considering.
Individual training adds onto a player’s workload so be careful how much extra you ask of players, especially younger players who are still in early development.