SQL Hard Drive Config?
Your questions are very broad as you are touching a lot of topics in sql server. I am just going to provide you relevant links so you can understand the subject in a better way and at your own pace.


  Is it recommended to have the Trans Logs and DB logs (ldf) on separate spindles or can they be on the same?


Seperate spindles is the best recommendation. Read on When should you put data and logs on the same drive?


  Do Trans Logs and ldf logs write concurrently or one after the other?


Transaction log is your ldf file. Writes to the transaction log are sequential in nature and benefit by being isolated on to separate physical devices.

Read up on : Diagnosing Transaction Log Performance Issues and Limits of the Log Manager and Optimizing Transaction Log Throughput


  Regardless of your decision, though, use Perfmon after the system goes live and track the drive activity.  If one of the two arrays is being overwhelmed with load while the other one sits idle, then it’s time to rethink the decision.  


I would suggest :


RAID 1 for OS 
RAID 10 for data, logs and tempdb


Note that there are many other factors that will directly or indirectly affect your choice as to whether your workload is OLTP or DSS ?


For optimized I/O parallelism, use 64 KB stripe size. Read on Are your disk partition offsets, RAID stripe sizes, and NTFS allocation units set correctly?
Make sure to properly size the tempdb files 
Use DMVs and Perfmon to set a baseline and look out for spikes or drops in your baseline.
Make sure to Test Disk Performance
Make sure that once your backups are completed locally, you move it to a safe and secure location and test them for restores regularly. So in an event of a disaster, you can confidently recover your data.