You will have as many projects and tasks as you need and you will also have as few projects and tasks as you need.
I use projects to group my tasks accordingly:
Single Action Lists - for those miscellaneous one-off tasks. I have SALs for House, Work, Personal, Family, and a few others.
Projects - to hold a group of related tasks that will accomplish a certain goal. I have projects in different folders for House, Work, Family, Personal, etc.
Active projects - these are projects that are currently available for me to work on. Most of my SALs (containing one-off tasks) are typically in active state. Special projects (reseeding the garden, build porch deck, prepare birthday party for Dad) are usually set to On Hold. These special projects will be switched to Active status when I set a defer date (set defer date of “prepare birthday party” about 2 weeks before party time) or when I do my weekly review and determine that I can set an On Hold project to Active status.
On Hold (Someday/Maybe) projects - On Hold projects that are not currently active but will be waiting in the wings for me to work on eventually. As stated above, every new project is set to On Hold status. I already have enough on my plate with the currently active SALs and active special projects.
I might be on the extreme side. I have 9 folders containing 71 projects with 1029 tasks.
From this group, I have 25 projects with 47 actions that are available for me to work on. Everything else is set to “On Hold”.
Learning to use the project status (Active, On Hold) has helped me focus. I work on only active projects. I have different perspectives that can slice my projects/tasks into manageable list views for me to focus on.
Using the review function in OmniFocus keeps me well informed of all On Hold projects as well as Active projects. I can determine whether to put a project back into Someday/Maybe (on hold) or set it to active status.
Learn to use custom perspectives in the pro version to narrow your projects/tasks into digestible lists.