I need to create the following data structure in wp:

{
	"type": "log",
	"id": 21,
        "log_day_1": { // what does this object represent in piklist? a CPT or field?

	         "log_day_activity": [ // this is just the array of associated posts objects via piklist 
			{
			    "id": "25213",
                            "desc": "I did this on this day and time"
                        },
                      ]
}

as you can see from the comments in the object, I’m struggling a bit. Should I use a custom repeatable field for days or create it’s own post type.

Can piklist associate posts to a custom field and do it more than one on a post? If so, how? And are there any guides in terms of querying the post and it’s activities for any particular day?

Or do I need to create a post called “Log” Then a post called “days” and associate “log” with “days” and then “days with it’s respective activities?

The second option seems laborious but will do it if it’s the only way. Let me know what you recommend!