Summary
Valanciunas is a skilled center who has nice touch inside, as he is an efficient scorer around the rim and in the paint. He is big enough to bully smaller centers and get easy buckets that way. While he does have some ability to stretch the floor, he only takes about one three-pointer per game, so he isn't exactly someone that the defense is worried about from outside. Valanciunas is a very good rebounder on both ends of the court, with his defensive rebounding rate being particularly great.

Defensively, Valanciunas is a large body and knows how to be somewhat of a presence inside, but that's about it. He can block some shots, but he isn't an great rim protector. He also can get attacked in space or in pick-and-roll since he isn't very quick laterally. You really only want him playing drop coverage and he relies on his teammates to contest midrange pull-ups from behind when defending the pick-and-roll.

Valanciunas is a solid starting-center, but nothing more. He will be 30 years old when he hits free agency in 2022, so there will likely be a fear that his best days are behind him.
 
Cap Considerations
Valanciunas will be an unrestricted free agent with a $21 million cap hold and full Bird rights. As his cap hold exceeds the salary he will get in free agency, his cap hold is not really relevant. If the Pelicans re-sign Valanciunas, his cap hold will be replaced by his starting salary, and the Pelicans may still have some cap space available depending on his salary and what happens with their other free agents.

There's also a chance that the Pelicans operate over the cap in 2022 and retain their own free agents while having the full Non-Taxpayer MLE and the Bi-Annual Exception to add players.

If Valanciunas demands a starting salary of more than the full $10.1 million Non-Taxpayer Mid-Level Exception, only teams with cap space will be able to sign him, unless a sign-and-trade is worked out. It is possible that Valanciunas could be had for the full MLE.