Let's walk through creating a standard Build VM
Step 3 - Plan your users and service accounts
Initial MS documentation on this topic can be found here.
Plan ahead and give these accounts meaningful names but also keep in mind that you have a 15 character limit for the username. In LCS you will have a limit of 3 non-production environments plus 1 production environment. If you have plan on using all 4 on prem, you'll have a decision to make. You can use the same set of accounts for all environments or separate the accounts out for each environment to separate security concerns. If you plan on having 1 Production environment named PROD, plus 3 other non-production environments names TEST, UAT and MIGRATION, you should consider changing your Financial Reporting Application Service Accounts to be similar to Contoso\svc-PRODFRAS$, Contoso\svc-TESTFRAS$, Contoso\svc-UATFRAS$ and Contoso\svc-MIGFRAS$. Below is the table from MS's document modified for a complete set of accounts for the TEST environment. The only call out here is that the local agent account as it his the 15 character max so we had to shorted LocalAgent to just LA.
|User account||Type||Purpose||User name|
|Financial Reporting Application Service Account||gMSA||Contoso\svc-TESTFRAS$|
|Financial Reporting Process Service Account||gMSA||Contoso\svc-TESTFRPS$|
|Financial Reporting Click Once Designer Service Account||gMSA||Contoso\svc-TESTFRCO$|
|AOS Service Account||gMSA||This user should be created for future-proofing. We plan to enable AOS to work with the gMSA in upcoming releases. By creating this user at the time of setup, you will help to ensure a seamless transition to the gMSA.||Contoso\svc-TESTAXSF$|
|AOS Service Account||Domain account||AOS uses this user in the general availability (GA) release.||Contoso\AXTESTServiceUser|
|AOS SQL DB Admin user||SQL user||Finance and Operations uses this user to authenticate with SQL*. This user will also be replaced by the gMSA user in upcoming releases.||AXTESTDBAdmin|
|Local Deployment Agent Service Account||gMSA||This account is used by the local agent to orchestrate the deployment on various nodes.||Contoso\Svc-TESTLA$|