You can use either 3100 (drawings) and 3300 (capital introduced), in which case your entries look fine. Or, you can use 1202 for everything. The difference is that 1202 is a “bank” account in the chart of accounts, so you can just set up money in or out as a transfer to/from the business account to the proprietor’s account. If all you do is either put money in, or take lump sums out, 3100 & 3300 work fine. If, though, you want to pay a business invoice off using your own account, for instance, you could 1202 works better as QF recognises it as a bank account, so you can create a supplier payment, which you can’t do from 3100.
Whichever is easier for you really. You can always change later, or use a mixture. At year-end, you just add together those 3 accounts to get your drawings/capital figure for the accounts.
In terms of the monitor arm, if it’s less than £150, don’t bother using fixed assets, just use an overhead code instead (7000-7999 range).