APBRmetrics

In an attempt to back-fill my college basketball databases with more than general stats I was trying to figure out the differences in Per100 possessions and 'advanced' as they are listed on many of the websites, e.g. basketball-reference, RealGM

I noticed that some of the "Advanced" stats say "per 100 plays" such as:

Turnover percentage is an estimate of turnovers per 100 plays.

Meanwhile others like assists, blocks, dreb, and treb say:

Assist percentage is an estimate of the percentage of teammate field goals a player assisted while he was on the floor.
Block percentage is an estimate of the percentage of opponent two-point field goal attempts blocked by the player while he was on the floor.
Defensive rebound percentage is an estimate of the percentage of available defensive rebounds a player grabbed while he was on the floor.
Total rebound percentage is an estimate of the percentage of available rebounds a player grabbed while he was on the floor.

BPM is in the "advanced" section and is stated as such:

BPM

Box Plus/Minus (available since the 1973-74 season in the NBA); a box score estimate of the points per 100 possessions that a player contributed
above a league-average player, translated to an average team. Please see the article About Box Plus/Minus (BPM) for more information.

I have an image of a player card where you can see the differences.
https://ibb.co/edMc6Q

So I guess my question(s) are:
-- Is "Advanced" actual for a few stats (e.g. blk%, ast%, reb%) and "estimate per 100 possessions" for a few stats like turnovers and BPM? Maybe it takes in an average of how many turnovers per 100 possessions and then their % of that %?
-- Which is more 'accurate' as in terms of 'actual' vs 'estimate'?
-- Advanced seems to multiply each result by 100 as well -- ergo per 100 possessions?
-- Which are we more likely to have data for going back the furthest? -- probably has to do with how possessions or lineups are tracked to get the numbers? I'm fine with either, both are fairly close -- but want to be able to calculate either, and whichever I can calculate back the furthest in time would get my preference unless someone can point out inherent flaws/biases in one vs the other.

for reference:
http://www.basketball-reference.com/about/glossary.html
http://basketball.realgm.com/info/glossary

I think they're all estimated.
The Warriors play almost 10 more possessions per 48 min. when Curry is on the floor vs when he isn't. Presumably then, there should be a bigger denominator in Stl/100, Blk/100, for Curry than for Livingston.
http://www.basketball-reference.com/tea ... 17/on-off/ It looks as though their possessions are assumed to be proportional to their minutes.