Classic or Enhanced?
Enhanced is the easier starting point if you want built-in guidance. Classic begins with less of it visible. These are interface and presentation presets, not difficulty levels. Individual options remain adjustable through Escape → Options. Choose for readability rather than what supposedly marks an experienced player.
Keep quest tracking useful
Open the quest log with L and track the objectives you are doing next. Untracking keeps the quest in your log; abandoning is different. Check the map with M and read the quest text too. A marker alone cannot explain every prerequisite, floor or item you need.
Bags and action bars
One-bag view makes it easier to see space and supplies. Give frequent abilities, defensives and consumables deliberate places on your bars, leaving room for new tools. Check icons in the spellbook rather than discovering an unfamiliar binding during your first difficult fight.
Movement and comfortable keybinds
Keep a frequent combat ability and your main defensive within easy reach. Practice strafing, turning the camera and retreating against harmless targets. Do not replace every movement and combat binding at once; otherwise you cannot tell which change is causing trouble.
Choose the combat information you need
WoW Forever already includes extra combat tools such as a cooldown display and damage meter. Enable a tool when it answers a specific need. If it obscures a target or party frame, it is in the wrong place. Do not judge a fight by damage alone.
Test changes and keep a way back
Take a screenshot of your current setup before larger changes. Afterwards, try accepting a quest, looting, using a vendor, fighting and reading party frames. Revert the setting that failed. Do not delete configuration folders merely to fix one badly placed display.
A first test without rebuilding everything
Stand somewhere quiet and try selecting an enemy, finding an ability, opening the map, reading a quest and finding an item in your bag. If you repeatedly have to move windows, start with their position or size.
Then check a simple fight: can you see your target's health, your own health and key abilities at the same time? A useful layout puts information where you already look, rather than keeping the centre empty at any cost.
What does your role need to see?
Healers need readable party members and dependable target changes. Tanks need enemies, personal health and defensive tools in view. Damage dealers need their target, position and interrupt or control tools.
Keep common controls consistent across characters if that suits you. Your map, bag and defensive tool need not move every time. Check each ability separately, though: similar icons can do very different jobs.
Change one thing at a time
Describe the problem first: too small, covering the target, distracting in combat or hard to reach. Change that one issue and repeat the same situation. You will know whether the adjustment helped.
Do not copy another layout blindly. Something designed for a large monitor may be hard to read on yours. Size text and controls for your normal sitting position.