In general across a roaming domain, try to stick to the same channel width. Due to most regulations are based on the EIRP, and it is spec'ed as a dBm/MHz Channel BW, the wider the channel is, the less energy you'll be transmitting with. On the other hand, the wider the channel is, the more bandwidth you'll have to push data, so you can push more at a time, in contrary to a more narrow channel bandwidth. You can think of it as a 2 lane highway versus a 16 lane highway. Your car may be traveling at the same speed, but you have a wider road, and thus more cars can drive at the same time.
On 5 GHz you have different bands, which all have different EIRP restrictions, and whether you may use them outdoors or not. So depending on what you need to may also need to consider which channels you are using. If you are near a harbor or an airport, you may also want to consider whether to use DFS channels or not. If an AP hears a radar, it will immediately stop serving clients on DFS channels and go into a listening state where it waits for 600 seconds! So if you have APs using a DFS channel it will suddenly stop serving, will do so for up to 10 minutes, and clients connected to that AP will do a hard roam. So channel planning is also a factor you may want to consider.
The first step towards this would be to configure the allowed channels to use in the RF profile. You can keep it to Auto, and the APs will assign channels themselves, but you can define certain channels to avoid.
One thing to keep in mind though, is that if an AP is unable to adhere to the configured channel list and width, it will select a lower width to "fit in". E.g. if you have configured a 40 MHz channel width, if the AP can not find a 40 MHz channel it will "degrade" to a 20 MHz channel. I've seen this for a fact on Cisco Classic - not sure if it's the same on Meraki but for CW APs, I'd assume so.
Also, I tend to disable all 802.11b rates, but setting the minimum til 12 Mbps. 11b rates use DSSS/FHSS, which doesn't utilize airtime very efficiently. From 12 and up, you get OFDM, which is more efficient. Wireless tenders to the lowest common denominator, so if one client chooses to use 11b rates and DSSS, it will bring down all other clients. So instead of allowing that to happen I simply disable 11 Mbps and lower.
Of course, as with everything else in networking, there are exceptions. So whether to use wider channels and higher rates - it really depends on your environment.
For an office setting, higher rates are ideal. Here 24 Mbps might be a better choice, so that the wireless network performs better.
But if you are designing wireless in a warehouse or a more challenging environment RF-wise, you may actually want to enable 11b rates. Because, while 11b rates are slower and not that efficient, they are more robust. In a warehouse setting, you'll often times won't have the need to push lots of data continuously, but maybe have more smaller bursts of data. So speed isn't a factor. You'll often also have a challenging environment with metal shelving, HVAC systems, reinforced concrete walls, tin roof and so on. All these have a negative impact on SNR, which certain higher datarates require.
In an office setting, you don't necessarily require robustness as much, as you would in a warehouse. In contrary you won't require speed as much in a warehouse setting as you would in an office.
I usually copy the pre-defined profiles and default to 12 Mbps rates on 2.4, 5 and 6 GHz.
40 MHz ChW on 5 GHz, and 40 or 80 MHz ChW on 6 GHz, depending on what mood I'm in..
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