Okkels wasn't a traditional winger like Morris - he wasn't going to skip by players and put in crosses. I don't recall him having much pace either. His game was to sit wide, exchange passes, track back when the left-back had gone forward, and play almost as an inside forward; arriving late into the box. He didn't really excel in the role, but it clearly was successful under Thelin in Sweden so has worked before.
I think Thelin is looking for a similar type of player, and if Okkels' transfer fee wasn't so high he'd probably sign him long term.
Besuijen is a similar player - he probably has more to his game than Okkels and has more experience of Scottish football.
The only doubt over him is his injury record. If he can't prove his fitness he'll be gone in summer, but he was back training towards the end of the season so here's hoping pre-season goes his way and he could be like a... I'm not going say it.