This is likely to be very time consuming to look at in detail, my general impression is that the points made are:
1. There are various neurological complications from covid 19 mainly in those who have been in ITU on a ventilator, and these had a number of pathologies, strokes, toxic confusion, encephalopathies, and perhaps a small minority specific encephalitis due to covid 19. This is probably the same rate of complications that you would see with anyone who has been in ITU and due to hypoxia, hypercoagulability and some immunological reactions.
2. These are mainly observational case reports, often there is no proper control group nor is there a strict denominator, so it is difficult to reach a conclusion as to how much a problem this is, and also how much a problem this is specifically in relation to covid-19.
3. I tried to read this preprint Adam Hampshire et al, ICL, I am not sure whether it will be accepted for publication but to me at least it has several problems. The data is based on an online questionnaire run by the BBC horizon program and therefor all the data is based on what the responders say, including whether they had a confirmed covid-19 test. Of course there is no control group and there is apparently no way to check on the accuracy of any of the data. It would be interesting to see if it is published, and if so, what the reviewers comments are.
In a situation like this there is a major bandwagon effect and a lot of observational studies where doctors and scientists observe some unusual complications and report them. Many of the reports are cautious to say things like, this warrants further investigations and so on. Given for example that the population at risk of severe covid 19 are also prone to strokes and cardiovascular events, to is very important to control for these factors. But claims that it ages you by ten years and you loose 8.6 percent of your IQ smack a bit like sensationalism.