It's going to be a shock going from declarative DSLs like Puppet and Terraform to a real coding language! Most of my coding experience has been in shell scripting and some Perl/Ruby from ages ago.
resources: [`arn:aws:${cdk.Aws.AccountNubmer}`]
(I know I got the arn format wrong and probably messed up the account number, but you get the gist I hope)
The reason is if you follow those rules strictly enough, you can still deploy that template in most accounts (dev, test, prod and so on), which has always been one of the core strengths of CF (and others) when done properly.
And I prefer to NOT use If statements in typescript if it can be done in Cloudformation with conditions or other items. For instance, if you only want to deploy a secondary rds slave in prod, use a CF condition and not a typescript 'if (accountNumber === myProdAccount)' because that means your typescript needs to know which account it's synthing for, which by default it does not.
IOW, try to use typescript to build DSL that's still in the spirit of DSL and you'll avoid a lot of traps that novices get themselves into.
Being able to throw in some loops here and there is quite a simplification on its own.