We should be able to view the impact on your current stats when you select a mod to view in your mod selection menu in-game. This will allow you to see the potential impact of certain mods and their interactions with your existing mods, and at the same time make it easier for new players to learn the game. All values will be calculated as if you chose that mod on your current stats.
Stat comparisons will also be color coded, where beneficial ones are green, detrimental ones are red, and situational ones are yellow.
Let's suppose that you have a run where you have all default gear, and you chose Magnitude as your first mod. This is what the mod would look like:
M A G N I T U D E
♦ +20% Projectile Size
♦ +15% Weapon Damage
♦ +5% Blast Radius
♦ Projectile Size: 100% ▶ 120% (+20%)
♦ Damage: 17 ▶ 19 (+15%)
♦ Blast Radius: N/A (Weapon does not possess Blast Radius)
(Note: Assuming here that blast damage requires mod Blast Radius)