Word of Warning
There may actually be no way you can have you cake and eat it, the pay and conditions are subject to the requirements of the job. you may be able to ask for a lower position but with that position will be lower pay (it may still be on more than your old job but less than this TL job).
Its also worth noting that doing a job badly can have very bad repercussions compared to turning down that job and not doing it at all, if you are genuinely not ready for the role, then it may be worthwhile just turning the job down outright.
Meat of the matter
Something non committal but also not rejecting might be the best bet here, as you have already "faked it in the interview" so you don't want to make problems before you even start in the role
Hi [insert boss's name], in regards to the requirements of my new role, I just wanted to clarify a couple of points: will there be any staff under me? and will I be required to carry out performance reviews or any other minor HR roles? i only ask as I've had plenty of one on one meetings with managers, but I've not had to any experience sitting on the other side of the table. You may have been able to tell in my interview while my technical abilities are very good, i do not have much experience in the managerial role and this concerns me.
This sets out that you are aware that you'll need to perform some of these roles but doesn't shut them down immediately, as you've said you faked it in the interview so you don't want to appear as to have lied to your new boss. but it also sets out in advance that your social abilities are indeed a concern which means your boss has been made aware of it, this should help steer the conversation towards a situation where you can either attempt to change the conditions for your new role or ask for a lower position.
I'm Sorry [insert boss's name] I've thought about it a lot and while i would really like the opportunity to work for you, I'm worried my Social skills don't match the requirements that my team would need.
This makes it look like you are more concerned for the team then with the role, this shows you have a moral compass and is a gentle and polite refusal of the job. but also makes you look good to your new boss, i would avoid following it up straight away with "is there any chance i can work in a less senior role" too quickly as your boss will likely want to think about it for a short while, instead give him a minute and see what he says, if he offers to adjust your terms of service then discuss it and arrange whats best for you, but try to think about whats best for him/her as well and meet somewhere in the middle. if they're annoyed that time has been wasted then you should just thank him for his time and walk away. leave it a day or two and then email offering your sincere apologies and ask that they keep your CV and should a less senior position open up to consider you.
You could follow up the first paragraph with a small section about wanting to be trained for these roles if they are indeed part of your new position.
I know the role requires me to be an Technical Adviser to junior members of the team and conduct reviews, this is my weakest skill for this position and was wanting to see if there was any training available to help me improve that.
This I admit would only really be for the HR tasks that Leads often have to perform but you may find it helpful and after some time you might find that you are able to perform these roles without issue.
Don't knock it till you've tried it
You've said you plan to fake it till you make it. its not impossible that once you've been in the role for a few weeks you find the social requirements of the job are a lot less then you expect and actually you're able to manage you awkwardness perfectly fine. the above note however might stand you in good stead as your boss know to look out if for you if you do struggle at any point in the leadership role.