I have a character concept for AL, but would like to pick and choose somethings between different backgrounds.

For a simple example I have a Lizardfolk Druid that was a member of a noble's army. The noble has given his tribe "possession" of a swamp in his lands in exchange for conscripts for the standing army and keeping the swamp free from enemy encroachment. For this character I want the Soldier background - but rather than the Military Rank feature (not sure how useful this would be in AL and also figure that even though he is a soldier, they wouldn't have gave him the high rank needed for the perk), he was a scout, so I would rather take the Outlander's Wanderer feature instead.

I have thought about taking the Outlander background and just saying he was a soldier, but like him having the Soldier background.

The problem is I don't know how strict AL is with backgrounds and don't want to show up at the table and be told that isn't allowed. I have played AL before, but do not have the time for the weekly games to ask someone there. I will be playing at a convention.

Also how do they do if you switch out tool proficiencies for different tool proficiencies or languages to tweak the background more to your liking?

You may create a custom PHB-valid Background for use in Adventurer's League

From the FAQ:

Can you create a customized background for your character?

Yes, you can customize backgrounds per the rules in the Player’s Handbook, which state that you can pick any two skills and a total of two tool proficiencies or languages. In addition, you can select a feature from any background.You can choose an equipment package from a background or spend gold on gear as normal.

The Player's Handbook provides these rules at the end of its section on Backgrounds (which also appears here in the basic rules):

Customizing a Background

You might want to tweak some of the features of a background so it better fits your character or the campaign setting. To customize a background, you can replace one feature with any other one, choose any two skills, and choose a total of two tool proficiencies or languages from the sample backgrounds. You can either use the equipment package from your background or spend coin on gear as described in chapter 5. (If you spend coin, you can't also take the equipment package suggested for your class.) Finally, choose two personality traits, one ideal, one bond, and one flaw.

If you can't find a feature that matches your desired background, work with your DM to create one.

I found it. Should have rechecked the Adventurers League's Player’s Guide first rather than relying on memory.

On page 2 under Step 4: Describe Your Character

Describe your character and choose a background.
Background. Choose or create a background using the Player’s Handbook or any of the resources above.

Per the Step 4 of Character Creation in the Adventurers League Player’s Guide v7.0 from the Player's Pack:

Background. Choose a background using the rules in the PHB or any other officially-released Wizards of the Coast or D&D Adventurers League resource. Your background isn’t limited to your character’s “PHB+1.”

The PHB has an option for a custom background, allowing you to pick a combination of proficiencies (two skills, plus a combination of two languages or tools). You're still limited to the published background features (like Outlander's "Wanderer" or Soldier's "Military Rank"), but the other selections are more flexible.