An LLC is a business entity. Subchapter S is a designation used for tax purposes. You have to ask the IRS for a subchapter S designation. That means, despite you are an LLC or other designation you will be treated as a corp for tax purposes. You have to track a little more stuff for tax purposes, but not nearly as much as a C corporation. Also, S chapter profits/losses flow to your personal income taxes which is less than C corps or sole proprietors.
One advantage is that you can take a REASONABLE salary and if you have profits at the end of the year you can take a distribution. You have to pay income tax on distributions, but not SS or Medicare. (You may remember the pissing contest between Trump and Biden about not paying taxes. This is what they both were doing. They were not avoiding INCOME taxes, but were LEGALLY avoiding SS and Medicare taxes).
You will have to hold an annual meeting if you are S chapter. You will have to have a board of directors, relatives will do. You will note that most corp annual meetings are held in very nice places. Don’t go apeshit with it and keep the meeting minutes, which amount to open the meeting, new items, old items, close the meeting.
You are also an EMPLOEE of the corporation. I encourage you to have a corp mailbox and phone other than your regular business phone. Why? When you are applying for credit you are officially an employee and you get better treatment. Why the phone and mailbox? Because if the bank sees the mailing address and phone for the corp is the same as your personal one they treat you as a sole proprietor/partnership and getting loans just got infinitely harder. Not talking about business loans, but car loans, loans for home improvements etc.
Your accountant can tell you more of the ins and outs. Here is a great article. To understand the article be sure you understand the first section, that an LLC is a business entity and subchapter S is a TAX designation.
 https://www.legalzoom.com/articles/s-corp-vs-llc?utm_source=google&utm_medium=cpc&utm_term=llc%20or%20s%20corp&utm_content=651761990571&utm_campaign=SMB%20|%20Overlap%20|%20Broad&utm_campaignID=19698563726&utm_adgroupID=149133323707&utm_partner=googlesearch&gad_source=1&gclid=Cj0KCQiAgK2qBhCHARIsAGACuzls5Xn47wg-tg0ZQ3BDXU3o332L3Q9o_OFIAhhwt-xakCxeJTyzeZEaAi7OEALw_wcB