There are three issues with traffic shaping your download
You can't force the senders to slow down, but you can influence them
The latency between the shaper and you is much lower than the shaper and them. It takes them longer to respond.
You're going from a faster to slow link when you shape your upload. Shaping your download is going from a slow to fast link.
Addressing #1. You can't stop bad actors. They can take several forms, the most common being a DOS attack. Nothing you can do with your firewall if they consume all of your bandwidth. There's another kind of bad actor. An example is many cable companies have horrible amounts of bufferbloat, which can cause the latency between you and someone else to be incredibly high. This can cause a sender to retransmit data that wasn't lost, but the latency was so high, it triggers a resend.
#2 and #3 are your most common. You biggest enemy is TCP ramps up exponentially. This means you need enough breathing room to keep your link from getting flooded. If you have a good connection, you can probably set your upload to 98% and effectively traffic shape. With your download, you may need to set it to 95% or lower.
Remember, PFSense shapes outgoing. You need to shape the outgoing of your LAN. Multi-LAN gets messy and has limitations.